REFRACTIVE  AND  OPHTHALMIC  CATECHISM 


FOR  THE  USE  OF 


General  Practitioners,  Opticians  and  Students, 


BY 


LAWRENCE  J.  DAILEY,  M.  D. 


Formerly  assistant  in  the  Eye  Department  of  the  Post-Gradoate  Medi- 
cal School  and  Hospital,  New  York  City,  member  of  the  New 
York  County  Medical  Association,  member  and  ex-presi- 
dent of  the  Fulton  County  Medical  Society,  Oph- 
thalmologist   and    Otologist    to  the  Nathan 
Littauer  Hospital,  Gloversville,  N.  Y. 
Etc. 


Gloversville,  N.  Y. 

Collins  Publishing  Company. 

1898. 


Cf7^^(:'^f 


COPYRIGHTED  1898 

BY 

L.  J.  DAILEY,  M.  D. 


oPro 


PKEFACE. 

In  offering  this  little  book  to  those  who  are  in- 
terested in  refractive  work,  it  is  in  the  hope  that 
the  author  has  succeeded  in  producing  a 
work  that  will  be,  first  of  all,  practical  and  accur- 
ate in  its  methods  of  determining  and  correcting 
the  different  refractive  conditions. 

It  makes  no  pretensions  beyond  being  a  con- 
cise and  ready  hand-book  on  the  subject  of  refrac- 
tive errors,  and  the  instruments  used  in  the  work. 
It  has  been  the  aim  all  through  to  use  the  ver}^  sim- 
plest language  and  terms  consistent  with  an  ac- 
curate description  of  the  subject  matter.  From 
the  standpoint  of  the  general  practitioner,  in 
which  field  the  author  labored  for  nine  years  pre- 
vious to  taking  up  special  w(^rk,  he  hopes  he  has 
succeeded  in  presenting  this  subject  to  others  in 
such  a  manner  as  to  enable  them  to  learn  some- 
thing about  refractive  errors  and  glasses  without 
the  necessity  of  reading  several  tomes — which  as  a 
rule  they  have  not  the  time— and  consequently 
learn  very  little  about  the  eye,  many  times  to  the 

3 


4  PREFACE. 

detriment  of  their  patients,  as  well  as  to  them- 
selves. In  this  particular  does  the  author  hope 
that  the  chapter  on  the  Diseases  and  Therapeutics 
of  the  Eye  will  prove  especiall}^  helpful. 

To  those  who  make  a  specialty  of  i^rescribing 
correcting  glasses,  and  especially  to  the  large 
number  of  opticians  engaged  in  this  work  does 
the  author  recommend  this  book  as  embodying  the 
most  practical  and  latest  methods  of  determining 
refractive  errors.  The  catechismal  arrangement  of 
the  work  was  adopted  principally  for  the  purpose 
of  keeping  the  subject  down  to  the  very  foundation 
of  practicability,  and  allowing  nothing  of  a  theo- 
retical nature  to  creep  in,  as  there  are  already 
plenty  of  works  on  theory  and  practice  that  can  be 
consulted  by  those  who  desire  to  extend  their 
knowledge  on  this  subject. 

I  am  under  great  and  lasting  obligations  to 
my  friend  and  teacher,  Professor  Francis  Valk,  of 
the  Post-Graduate  Medical  School  and  Hospital, 
New  York  City,  for  his  kindly  advice  and  intelli- 
gent instruction  during  the  years  of  1891  and  1892, 
when  it  was  my  good  fortune  to  be  his  assistant, 
and  acknowledge  the  help  I  have  received  from 
his  well  known  work  on  refraction. 

Also  to  Prof.  D.  B.  St.  John  Rossa,  for  the 
early  instruction  I  received  from  him  while  a  stu- 


PREFACE  5 

dent  in  the  medical  department  of  the  University 
of  the  city  of  New  York  in  the  years  of  1880,  1881 
and  1882,  where  I  found  it  a  great  pleasure  to  at- 
tend his  clinics  at  the  college,  as  well  as  ten  years 
later  at  the  Manhattan  Eye  and  Ear  Hospital. 

I  hereby  acknowledge  my  obligation  to  those 
who  so  kindly  furnished  me  some  of  the  cuts, 
wliile  others,  mauy  of  which  were  selected  from 
various  standard  works,  I  acknowledge  both  here 
and  in  the  text.  The  glossary  found  in  the  conclu- 
sion of  the  book,  will,  it  is  hoped,  prove  a  valuable 
aid  in  the  study  of  this  subject. 

In  hoi)es  that  this  little  catechism  will  prove 
a  friend  to  all  interested  in  this  work,  either  as 
student,  i)ractitioner  or  optician,  the  author  offers 
it  as  a  recruit  in  the  missionary  field  of  ophthalmic 
science. 

Gloversville,  N.  Y.,  Sept.,  1898. 


CONTENTS. 


CHAPTER  I. 
Anatomy  of  the  Eye,       ..----.-9 

CHAPTER  II, 
Refraction  and  Lenses,  ...--.-      18 

CHAPTER  III. 
Accommodation  of  the  Eye,  35 

CHAPTER  IV. 
Emmetkopia  and  Hypermetropia, 39 

CHAPTER  V. 
Myopia, 49 

CHAPTER  VI. 
Astigmatism,        ....       - 58 

CHAPTER  VII. 

Ophthalmoscopy,       ...       - 78 

CHAPTER  VIII. 

Ophthalmometry, 96 

CHAPTER   IX. 

Skiascopy,  Retinoscopy  or  Shadow  Test,       -        -        -        -     106 

6 


CONTENTS.  7 

CHAPTER  X. 

Presbyopia, 123 

CHAPTER  XI. 

Muscular  Asthenopia, -        -     131 

CHAPTER  XII. 

Perimetry, 150 

CHAPTER  XIII. 
Illustrative  Cases  From  Note  Book,  .       .       .       .    156 

CHAPTER  XIV. 
Diseases  and  Therapeutics  of  the  Eye,      -        -        .        .    182 

Glossary,    - 199 

Index, 210 


CHAPTER  I. 


Anatomy  of  the  Eye. 

Q.  What  is  the  anatomical  location  of  the 
eye? 

A.  It  is  located  in  the  anterior  portion  of  the 
skull,  in  the  cavity  of  the  orbit,  which  is  a  cone- 
shaped  cavity,  formed  by  several  of  the  cranial 
bones. 

Q.     What  is  the  depth  of  this  cavity? 

A.  It  is  about  one  and  three-quarters  of  an 
inch  deep. 

Q.  Which  way  are  the  bases  of  the  orbital 
cavity  directed? 

A.     Forward  and  outward. 

Q.     What  purpose  do  the  orbits  serve? 

A.  By  their  strong,  bony  walls  they  give  pro- 
tection to  the  eyeballs,  and  by  the  connective  tis- 
sue and  fatty  matter  contained  in  them,  they  af- 
ford a  cushion-like  bed  for  the  same,  thus  permit- 
ting of  their  free  movement  in  any  direction. 


10    ■  REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

In  front  they  give  attachment  to  a  strong  cir- 
cular muscle,  called  the  orbiculares  palpebrarum, 
and  the  eye-lids,  which  afford  comparative  secur- 
ity to  the  eye-ball  at  its  base. 

Q.     What  is  the  size  and  shape  of  the  eye-ball? 

A.  It  has  an  antro-posterior  diameter  of 
about  one  inch  and  a  transverse  diameter  some- 
what less.  It  is  spheroidal  in  shape, with  a  segment 
of  a  lesser  sphere  for  its  anterior  surface,  or  the 
cornea,    which    is    transparent    and    constitutes 

about  one-sixth  of  the  globe. 
Figure  1. 


Vertical    section    of    the    eye    ball,     showing     the    three    coats 

or  tissues,   the  diopric  media,   ciliary  processes  and  muscle 

as  well  as  capsule  of  the  the  lens.     (After  Gray). 

Q.     Of  what  is  the  eye-ball  composed? 

A.     It  is  composed  of  three  coats,  or  tunics, 


ANATOMY  OF  THE  EYE.  11 

and  both  fluid  and  solid  refractive  media   called 
humors. 

Q.     What  are  the  coats  or  tunics  called? 

A.  The  sclerotic,  and  its  continuation  in 
front,  the  cornea;  the  choroid,  with  its  appen- 
damages,  the  iris,  and  ciliary  jDrocesses;  and  the 
retina, 

Q.  What  are  the  names  of  the  refracting 
media? 

A.  From  before  backwards,  the  cornea,  the 
aqueous  humor,  the  crystalline  lens,  and  the  vi- 
trious  humor. 

Q.  What  is  the  character  of  the  sclerotic 
coat,  or  tunic? 

A,  It  is  a  hard,  firm,  dense  membrane,  giv- 
ing shape  to  the  eye-ball,  and  attachment  to  the 
various  muscles  of  the  globe  or  eye-ball. 

Q.  What  are  the  characteristics  of  the  sec- 
ond coat,  or  choroid? 

A.  It  is  a  thin,  highly  vascular  and  pigment- 
ed membrane,  which  invests  about  five-sixths  of 
the  globe.  It  is  composed  of  three  layers,  the  ex- 
ternal, middle,  and  internal.  The  ciliary  pro- 
cesses are  formed  by  the  folding  of  the  middle  and 
internal  layers  of  the  choroid,  and  are  attached  to 
the  crystalline  lens  by  means  of  the  suspensory 


12      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

ligament.  The  iris,  which  is  formed  from  the 
choroid  coat,  receives  its  name  from  its  various 
colors,  and,  in  this  respect  from  its  resemblance  to 
a  rainbow.  It  is  a  thin,  circular  curtain,  or  dia- 
phragm, suspended  anterior,  to  the  crystalline 
lens  with  a  circular  aperture,  called  the  pupil.  Its 
function  is  to  regulate  the  amount  of  light  admit- 
ted into  the  chamber  of  the  eye. 

Q.     What  is  the  ciliary  muscle? 

A.  A  small,  circular  band  about  one-eighth 
of  an  inch  broad,  on  the  anterior  surface  of  the 
choroid.  It  is  the  principal  muscle  of  the  accom- 
modation of  the  eye. 

Q.  What  is  the  retina,  or  the  internal  coat 
of  the  eye-ball? 

A.  It  is  a  very  thin,  delicate,  nervous  coat, 
upon  the  surface  of  which  the  images  of  external 
objects  are  received.  It  is  composed  of  several 
layers,  but  the  first  layer,  or  the  layer  of  rods  and 
cones,  is  mostly  concerned  in  the  phenomenon  of 
sight. 

Q.  What  are  the  physical  characteristics  of 
the  dioptric,  or  refractive  media? 

A.  Of  the  cornea,  and  lens,  transparency, 
density,  elasticity;  and  of  the  lens,  adjustability 
and  their  freedom  from  bloodvessels.    Of  the  aque- 


ANATOMY  OF  THE  EYE.  13 

ous  and  vitrious  humors,  semi-fluidity  and  trans- 
parency, and  of  all,  refractability. 

Q.  If  they  are  free  from  blood-vessels,  how 
do  they  receive  their  nutrition? 

A.  By  imbibition  or  absorption  from  the 
surroundino-  tissues,  which  are  freely  supplied 
with  blood  vessels. 

Q.  How  is  the  crystalline  lens  held  in  posi- 
tion? 

A.  It  is  enclosed  in  a  capsule  which  is  thick- 
er in  front  than  behind,  and  is  retained  in  position, 
principally  by  the  suspensory  ligaments  of  the 
lens,  which  connects  the  anterior  margin  of  the 
retina  with  the  anterior  surface  of  the  lens. 

Q.     What  are  the  appendages  of  the  eye? 

A.  The  eye-lid,  eye-brows,  lachrymal  gland 
and  sac,  conjunctiva,  and  nasal  duct. 

Q.     What  are  the  angles  of  the  eye-lids  called  ? 

A.  They  are  called  the  outer  and  inner  can- 
thus. 

Q.  What  are  the  folds  of  the  conjunctiva 
called? 

A.  That  fold  covering  the  eyes  is  called  the 
ocular  conjunctiva,  and  that  portion  covering  the 
lids,  the  palpebral  conjunctiva. 


14      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Q.  What  sort  of  a  membrane  is  the  conjunc- 
tiva? 

A.     It  is  a  mucous  membrane. 

Q.  What  are  the  little  glands  found  on  the 
inner  surface  of  the  lids  called? 

A.  The  Meibomian  glands.  They  secrete  a 
mucous  to  lubricate  the  lids,  and  have  their  open- 
ings on  the  edge  of  the  lids. 

Q.  What  is  the  function  of,  and  where  is  the 
lachrymal  gland  located? 

A.  It  is  to  secrete  tears,  and  is  located  in  a 
depression  at  the  outer  angle  of  the  orbit. 

Q.  What  is  the  function  and  location  of  the 
lachmyral  sac  and  duct? 

A.  They  are  to  carry  off  the  tears,  and  are  lo- 
cated, the  former  at  the  inner  canthus  of  the  eye- 
lids: the  latter  is  lodged  in  a  groove  in  the  lachry- 
mal and  superior  maxillary  bone,  which  opens  into 
the  nasal  cavity. 

Q.     What  are  the  puncta  lachrymalia? 

A.  Two  little  openings  at  the  inner  part  of 
each  lid,  which  are  the  mouths  of  the  lachrymal 
sac.  They  are  slightly  elevated  above  the  surface 
of  the  lids. 


ANATOMY  OF  THE  EYE. 


15 


Q. 

orbit? 


How  many  muscles    are    there  in  each 


FiGUKE    2. 


Muscles    of    the    right    orbit,    showing    those    attached    to    the 

globe  of  the  eye  and  the  one  which  is  not  connected  with 

the  globe,  but  is  inserted  into  the   tarsal  border. 

(After  Gray.) 

A.  There  are  seven  altogether,  six  of  which 
are  attached  to  the  globe  of  the  eye, 

Q.     What  are  their  names  and  action? 

A.  Two  sui)erior  recti  to  turn  the  eye-balls 
up.  Two  inferior  recti  to  turn  the  eyes  down. 
Two  internal  recti  to  turn  the  eyes  in,  and  two  ex- 
ternal recti  to  turn  the  eyes  out.  Then  there  are 
the  superior  and  inferior  oblique  muscles  which 
rotate  the  eye-ball  on  its  antro-posterior  axis. 

Q.  What  are  the  principal  blood-vessels  of 
the  eye? 


16       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

A.  The  principal  artery  is  the  ophthalmic, 
which  is  a  branch  of  the  internal  carotid  artery  af- 
ter that  vessel  passes  through  the  skull.  The  oph- 
thalmic artery  gives  off  two  groups  of  branches, 
the  ones  that  supply  the  orbit,  called  the  orbital 
group,  and  the  branches  tliat  supply  the  muscles 
and  globe  of  the  eye,  called  the  ocular  group.  A 
small  branch  of  the  latter,  the  arteria  centralis 
retinae,  pierces  the  optic  nerve,  and  passes  inward 
through  the  center  of  the  nerve  to  be  distributed 
to  the  retina,  as  far  forward  as  the  ciliary  pro- 
cesses. 

Q.     What  are  the  nerves  of  the  eye? 

A.  They  are  the  second,  third,  fourth  and 
sixth  cranial  nerves.  The  second,  or  optic  nerve, 
is  the  special  nerve  of  the  sense  of  sight.  The 
third,  also,  called  the  motor  oculi,  supplies  all  the 
muscles  of  the  orbit  except  the  external  rectus  and 
the  superior  oblique.  The  fourth,  or  trochlear 
nerve,  supplies  the  superior  oblique  muscles, 
while  the  sixth,  or  the  abducens,  supplies  the  ex- 
ternal rectus  muscle. 

Q.  What  mechanical  instrument  is  likened 
unto  the  eye? 

A.  The  camera  obscura.  The  retina  of  the 
eye  corresponding  to  the  sensitive  plate  of  the 


ANATOMY  OF  THE  EYE.  17 

camera.  Its  function  is  to  receive  visual  impres- 
sion and  to  convey  them  to  the  optic  nerve,  which 
in  turn  conveys  them  to  the  brain. 

Q.     What  is  this  phenomenon  called? 

A.     Tt  is  called  sight,  one  of  the  special  senses. 

Q.  Are  all  portions  of  the  retina  equally  sen- 
sitive to  these  visual  impressions? 

A.  They  are  not.  The  central  part  is  the 
most  sensitive. 

Q.     What  is  the  central  part  called? 

A.,  It  is  called  the  fovea  centralis  retinae, 
the  depressed  portion  of  the  maculae  lutea,  or 
"yellow  spot,"  as  it  is  called  frequently.  It  is  lo- 
cated at  the  temporal  side,  and  on  a  level  with  the 
lower  border  of  the  optic  disk,  and  it  can  be  recog- 
nized with  the  ophthalmoscope,  principally  by  the 
absence  of  blood-vessels  in  its  vicinity. 


CHAPTER  11. 


Refraction  and  Lenses. 

Q.     What  is  meant  by  refraction? 

A.  That  change  which  takes  place  in  lumi- 
nous rays  as  they  pass  from  one  medium  to  anoth- 
er of  greater  density. 

Q.  What  medium  is  used  as  a  standard  of 
measurement? 

A.  Air  is  used,  with  an  index  of  refraction  of 
1,  as  a  standard. 

Q.  What  change  takes  place  in  rays  of  light 
in  passing  from  the  air,  say,  to  one  of  greater  den- 
sity, and  hence  greater  refractive  power? 

A.  All  the  rays  striking  the  denser  medium 
oblique,  are  bent  towards  the  perpendicular  of  the 
refracting  medium,  while  the  rays  striking  the  re- 
fracting body  perpendicular  to  its  surface,  pass 
through  without  undergoing  any  change. 

Q.  What  is  meant  by  the  term  "index  of  re- 
fraction" in  this  connection? 

18 


REFRACTION  AND  LENSES.  19 

A.  It  means  the  relative  power  possessed  by 
different  refracting  media  of  bending  oblique  rays 
toward  the  perpendicular  when  passing  from  a 
lighter  medium  like  air,  into  a  denser  one  like 
glass,  for  instance. 

Q,  Are  there  many  substances  found  pos- 
sessing this  power  of  refracting  rays  of  light? 

A.  Yes;  they  are  found  to  exist  in  large  num- 
bers in  solids,  liquids  and  gases. 

Q.  What  are  the  refractive  indices  of  quartz 
and  crown  glass  used  in  lenses  for  the  correction  of 
refractive  errors  found  to  exist  in  the  eye? 

A.     About  1.5,  as  compared  with  air  as  1. 

Q.  What  are  the  refractive  indices  of  the  di- 
optric or  refractive  media  of  the  eye,  that  is,  the 
cornea,  the  aqueous  humor,  the  crystalline  lens, 
and  the  vitrious  humor? 

A.  For  the  cornea,  aqueous  and  vitrious  hu- 
mors, about  1.33;  while  the  crystalline  lens  has  a 
refractive  index  of  1.47. 

Q.  What  are  the  glasses  used  in  correcting 
errors  of  the  refractive  media  of  the  eye  called? 

A.     They  are  called  lenses. 

Q.  How  many  kinds  of  lenses  are  there  as  re- 
gards their  action  on  rays  of  light? 


FiGUBE  3. 


1        8      3      4        5       6 


1. 

2. 
other . 

3. 

4. 


Double  Convex  Lens — Convex  on  both  surfaces. 
Piano-Convex — Plane  on  one  surface  and  convex   en  the 


Double  Concave — Concave  on  both  surfaces. 

Piano-Concave — Plane    on    one  surface  and    concave    on 
the  other. 

5.  Convexo-Concave — Convex  on  one  surface  and  concave  on 
the  other,  more  convex  than  concave,  making  it  a  plus  lens. 

6.  Concavo-Convex — Concave  on  one  side  and  convex  on  the 
other,  more  concave  than  convex,  making  in  a  minus  lens. 
These  lenses  are  also  called  periscopic  meniscus  lenses. 

7.  Prism  Lens. 

8.  Convex  or  Plus  Cylindric  Lens. 

9.  Concave  or  Minus  Cylindric  Lens. 


REFRACTION  AND  LENSES.  21 

A.  Two  kinds,  namely:  the  lenses  which 
converge  or  bring  rays  of  light  to  a  point,  or  focus, 
and  the  lenses  that  cause  a  divergence  of  the  rays 
after  passing  through  them. 

Q.     What  other  names  arethey  known  by? 

A.  Convex  lenses  and  concave  lenses.  The 
former  are  also  called  magnifying  glasses,  while 
the  latter  are  sometimes  called  minifying  lenses. 

Q.  What  signs  are  used  to  denote  these  dif- 
ferent kinds  of  lenses? 

A.  The  plus  sign  (-[-)  for  the  convex,  and  the 
minus  sign  ( — )  for  the  concave. 

Q.  How  many  different  forms  or  shapes 
have  each  of  these  two  kinds  of  lenses? 

A.  Three.  There  is  the  double-convex,  or 
concave,  which  is  convex  or  concave  on  both  sur- 
faces. There  is  the  plano-convex,  or  concave, 
which  is  plane  on  one  surface  and  convex  or  con- 
cave on  the  other,  and  there  is  the  convexo-con- 
cave, or  meniscus  lens,  which  is  convex  on  one  sur- 
face and  concave  on  the  other,  and  the  concavo- 
convex  which-is  concave  on  one  side  and  convex 
on  the  other.  These  two  last  kinds  are  also  called 
periscopic  lenses. 

Q.  How  can  you  readily  tell  whether  a  cer- 
tain lens  is  a  plus  or  a  minus? 


22      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

A.  By  holding  it  before  your  eye  and  looking 
through  it  at  some  fixed  object,  moving  it  slightly 
from  side  to  side  or  up  and  down.  If  it  be  a  plus 
lens,  the  object  will  move  in  an  opposite  direction, 
while  if  it  be  a  minus  lens,  the  object  will  move  in 
the  same  direction  as  the  lens.  This  is  the  simplest 
test. 

Q.  Under  what  general  name  are  the  above 
variety  of  lenses  known? 

A.  They  are  known  as  spherical  lenses,  be- 
cause they  are  obtained  by  sawing  a  section  off  a 
sj)here,  and  they  refract  rays  of  light  in  all  their 
different  meridians. 

Q.  And  are  there  lenses  which  do  not  refract 
rays  in  all  their  meridians? 

A.  Yes;  there  are  the  cylindric  lenses  which 
are  obtained  by  sawing  a  section  off  a  cylinder  of 
glass,  and  which  only  refract  light  in  one  meridi- 
an, which  is  at  right  angles  to  its  axis.. 

Q.  How  many  kinds  of  cylindrical  lenses  are 
there? 

A.  There  are  two  kinds;  the  convex  or  plus, 
and  the  concave  or  minus. 

Q.  How  can  we  readily  tell  whether  a  lens 
be  a  cylindrical  or  spherical? 


REFRACTION  AND  LENSES.  33 

A.  When  holding  it  before  the  eye,  and  look- 
ing at  an  object  at  some  distance,  the  object  moves 
only  in  one  direction  when  the  lens  is  moved  be- 
fore the  eye.  Tliat  is,  it  moves  against,  in  one 
meridian  if  it  is  a  plus  or  convex  cylinder,  and 
vi'ith,  if  it  be  a  minus  or  concave  cylinder. 

Q.  How  can  you  determine  the  axis  of  a  cy- 
linder lens? 

A.  Draw  two  straight  lines  on  some 
plane  surface,  a  sheet  of  paper  for  example, 
at  right  angles  to  each  other  in  the  form  of  a  cross, 
looking  at  these  lines  through  your  cylinder  lens, 
unless  they  correspond  with  the  axis  of  the  lens, 
they  will  appear  broken,  that  is  the  part  of  the 
line  passing  through  the  leng  will  not  be  continu- 
ous with  the  lines  beyond  the  edge  of  the  lens. 
Now,  by  turning  the  lens  until  the  lines  become 
continuous,  will  give  you  the  two  principal  meridi- 
ans of  the  lens,  and  the  meridian  in  which  there  is 
no  displacement  of  the  lines,  when  the  lens  is 
moved,  at  right  angles  to  this  line,  will  indicate 
the  axis  of  the  cylinder,  which  is  always  found  at 
right  angles  to  the  refracting  meridian  of  the  cy- 
linder lens. 

Q.  Do  plus  cylinder  lenses,  like  convex  spher- 
icals,  bring  parallel  rays  of  light  to  a  point  at  their 
principal  focal  distance? 


24      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

A.  They  do  not  form  a  point  like  a  spherical, 
bat  a  line  of  light  at  the  focal  distance,  owing  to 
the  refraction  taking  place  in  one  meridian  only, 
and  this  line  is  always  at  right  angles  to  the  axis 
of  the  cylinder. 

Q.     What  is  a  prismatic  lens? 

A.     A  prismatic  lens  is  a  portion  of  glass,  or 
other    transparent  substance,  included  between, 
two  plane  surfaces,  inclined  toward  each  other. 

Q,  What  is  the  action  of  a  prismatic  lens  in 
regard  to  rays  of  light? 

A.  Rays  are  bent,  or  refracted,  toward  the 
base  of  the  prism. 

Q.  What  is  meant  by  the  focal  distance,  or 
point,  of  a  lens? 

A.  It  means  the  point  at  which  parallel  rays 
of  light  are  brought  together.  This  is  called  its 
principal  focal  point,  which  is  the  inverse  of  the 
refractive  power  of  the  lens,  that  is,  a  lens  having 
a  refractive  power  of  40  inches  has  only  half  the 
refractive  power  of  a  lens  whose  focal  point  for 
parallel  rays  is  at  20  inches. 

Q.  What  is  used  for  a  standard  of  measure- 
ment in  numbering  the  principal  focal  point  of 
lens? 

A.     A  lens  whose  focal  point  is  at  one  metre, 


REFRACTION  AND  LENSES.  25 

or  about  40  inches,  also  called  a  dioptre,  which 
according  to  the  dioptric  or  French  method  of 
enumeration,  is  taken  as  a  standard. 

Q.  Are  all  lenses- numbered  according  to  the 
dioptric  system? 

A.  They  are  numbered  in  both  the  inch  and 
the  dioptric  systems. 

Q.  Are  these  two  systems,  that  is,  the  inch 
and  dioptric,  readily  convertible,  one  into  the 
other? 

A.  Yes,  very  readily,  as  it  is  simply  a  matter 
of  division  and  multiplication.  For  example,  if 
we  have  a  lens  whose  focal  distance  is  numbered 
in  inches,  say  10  inches,  and  we  wish  to  find  how 
many  dioptres  there  are  in  it,  we  simply  divide  40 
inches,  one  dioptre,  by  10  inches,  the  number  of 
the  lens,  and  as  we  have  seen  that  the  refractive 
power  is  the  inverse  of  its  focal  distance,  we  find 
we  have  a  lens  of  4  D.  40  inches  -f- 10  inches 
equals  4  D. ;  or  reversely,  if  we  have  a  lens  number- 
ed in  dioptres,  and  we  wish  to  find  out  its  focal  • 
length  in  inches, we  have  simply  to  divide  40  inches 
or  one  dioptre,  by  the  number  of  the  lens,  in  diop- 
tres, and  the  result  will  be  the  focal  point  in 
inches;  e.  g.,  we  have  a  lens  of  4  dioptres,  and  we 
wish  to  find  out  the  number  in  inches,  all  we  have 
to  do  is  to  divide  40  inches  4-  4D  equals  10  inches. 


26      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Although  this  does  not  always  result,  without  a 
small  fraction  remaining,  it  is  approximately  and 
sufficiently  correct  for  practical  purposes. 

Following  is  a  table  of  the  dioptric  system 

with  their  corresponding  number  in  English 
inches,  as  well  as  the  approximate  or  correspond- 
ing lens  of  the  old  system,  or  Paris  inch  of  27.07 
minutes,  according  to  which  many  of  the  trial 
cases  are  numbered: 

No.  of  lens 

in 
dioptres. 

0.12 
0.25 
0.50 
0.62 
0.75 
1.00 
1.25 
1.50 
1.75 
2.00 
2.25 
2.50 
2.75 
3.00 
3.25 
3.50 
4.00 
4.50 
5.00 
5.50 
6.50 


Focal  distance 

Focal  distance 

Corresponding 

in 

in 

lens, 

millimetres. 

English  inches. 

old  system. 

8,000 

314.96 

288 

4,000 

157.48 

144 

2,000 

87.74 

72 

1,600 

62.99 

60 

1,333 

52.50 

48 

1,000 

39.37 

40 

800 

31.50 

48 

666 

26.22 

24 

571 

22.48 

22 

500 

19.69 

20 

444 

17.48 

18 

400 

15.75 

16 

363 

14.31 

14 

333 

13.12 

13 

308 

12.11 

12 

285 

11.25 

11 

250 

9.84 

10 

222 

8.74 

9 

200 

7.87 

8 

182 

7.16 

7 

154 

6.06 

6 

wn  to  20  D. 

or  2". 

REFRACTION  AND  LENSES.  27 

Q.     How  are  prismatic  lens  measured? 

A.  Generally  by  their  angle  of  deviation, 
instead  of  their  refracting  angles.  There  are  two 
methods  used ;  the  first,  and  to  my  mind  the  easiest 
is  the  method  proposed  by  Mr.  Charles  F.  Pren 
tice  of  New  York  City,  the  well-known  optician, 
which  he  calls  the  prism-dioptre,  and  which  he 
uses  for  a  standard.  This  is  a  prism  which  shall 
reflect  a  ray  of  light  one  centimetre  at  a  plane  one 
metre  (39.37  inches)  distance.  The  second  method 
is  by  Dr.  W.  S.  Dennett,  who  takes  what  he  calls 
the  centrad  for  a  standard.  It  is  not  so  readily  un- 
derstood as  the  first  method. 

Q.  What  are  the  special  uses  of  the  different 
lenses  in  the  different  refractive  conditions  of  the 
eye? 

A.  The  convex  sphericals  are  employed  in 
hypermetropia,  where  the  antro-posterior  diameter 
of  the  eye  is  too  short.  Parallel  rays  do  not  come 
to  a  focus  on  the  retina,  but  behind  it,  as  it  were. 
As  a  convex  lens  converge  rays  to  a  point,  we  use 
it  in  hypermetropia  to  assist  the  eye  in  bringing 
the  rays  to  a  focus  more  in  front,  or  on  the  retina. 
Now,  in  myopia,  the  diameter  is  too  long,  so  the 
rays  are  brought  to  a  point  before  they  reach  the 
retina;  and  as  a  concave  lens  causes  a  divergence 


28      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

of  the  rays  of  light  passing  through  it,  we  use  it  in 
myopia  to  assist  in  bringing  the  rays  to  a  focus 
farther  back  on  the  retina.  The  cylindrical  lenses 
are  used  to  correct  astigmatism,  or  where  the  rays, 
entering  the  eye,  do  not  all  come  to  a  focus  at  the 
same  point  on  the  retina,  which  may  occur  in  ei- 
ther hypermetropia  or  myopia.  The  use  of  the 
prism  lens  is  confined  exclusively  to  the  correc- 
tion of  muscle  difflculties  arising  from  either  in- 
sujBflciency,  or  other  cause,  such  as  paralysis  or  in- 
juries. 

Q.  What  are  the  requisite  qualities  for  a 
good  lens? 

A.  It  must  be  made  from  clear  glass  or 
quartz;  it  must  be  carefully  and  equally  ground  in 
all  its  meridians,  and  it  must  be  accurately  cut  as 
regards  its  optical  axis  and  center. 

Q.  How  are  lenses  generally  arranged  for 
convenient  use  in  the  correction  of  the  errors  of  the 
refractive  media  of  the  eye? 

A.  A  series  of  the  different  kinds  of  lenses 
are  arranged  according  to  their  focal  power,  begin- 
ning with  the  weaker  numbers  and  running  up  in 
a  convenient  case,  many  varieties  of  which  are  to 
be  found  on  the  market.  A  well  equipped  trial 
case  contains  something  like  the  following  list  of 


REFRACTION  AND  LENSES. 


29 


lenses   and  accessories   found  necessary   in  this 
work : 

Figure  4. 


Audeinair's  Trial  Case,  made  by  the  Spencer  Optical  Co. ,  New  York. 

Thirty-five  pairs,  each  of  convex  and  concave 
spherical  lenses;  twenty-five  pairs,  each  convex 
and  concave  cylindric  lenses;  prisms  from  1  degree 
to  20  degrees;  colored  glasses,  three  kinds,  1  stene- 
optic  disk,  1  blank  disk  to  cover  one  eye,  while  the 
other  is  being  examined;  1  ground  glass  for  the 
same  purpose;  1  disk  with  small  hole;  1  adjustable 


30      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

trial  frame  with  double  cells;  and  1  single  cell,trial 
frame,  etc. 

Q.  What  is  the  result  of  combining  convex 
and  concave  lens? 

A.  One  will  neutralize  the  other;  for  exam- 
ple, if  we  take  a  convex  lens  of  2D.  and  place  it 
and  a  concave  lens  of  2D.  together,  one  will  neu- 
tralize the  other,  and  the  result  will  be  a  plane 
glass  having  no  refracting  power.  We  avail  our- 
selves of  this  neutralizing  power  when  we  wish  to 
measure  a  certain  lens  and  have  no  instrument  for 
that  purpose  at  hand.  In  measuring  a  cylindric 
lens  in  this  way,  the  axis  of  the  two  must  be  paral- 
lel. Of  course  we  use  the  numbered  lenses  of  the 
trial  case  in  this  procedure. 

Q.     What  is  meant  by  the  "visual  angle?"     , 

A.  It  is  the  angle  formed  by  lines  drawn 
from  the  two  extremities  of  an  object  to  the  nodal- 
point,  or  the  optical  center  of  the  eye.  This  point 
is  situated  about  15  millimetres  in  front  of  the  reti- 
na,and  about  7  millimetres  behind  the  cornea.  Rays 
of  light  directed  to  the  nodal-point  pass  through 
straight  without  undergoing  any  refraction. 
This  "visual  angle"  determines  the  size  of  the  reti- 
nal image  of  an  object,  which  in  order  to  subtend 
the  same  angle  on  the  retina  must  be  larger  the 


REFRACTION  AND   LENSES.  -     31 

farther  it  is  removed  from  the  eye.  The  size  of  the 
retinal  image  is  to  the  size  of  the  object  as  the  dis- 
tance from  the  nodal-point  is  to  the  retina;  hence, 
it  follows  that  the  size  of  the  retinal  image  in  hy- 
permetropia,  where  the  retina  is  nearer  the  nodal- 
point  of  the  eye,  is  smaller  than  in  emmetropia; 
and  that  in  myopia,  where  the  retina  is  farther 
from  the  nodal-point  than  in  emmetropia,  that  the 
retinal  image  will  be  larger. 
Figure  5.  ^       q^     What  is  the  normal  acuteness 

Eof  vision? 
A.  Snellen  determined  that  the 
normal  acuteness  of  vision  was  the 
power  of  distinguishing  letters 
formed  by  strokes  whose  width 
vas  one-fifth  the  size  of  the  letter, 
and  subtending  an  angle  of  5  min  - 
utes.    This  led  him  to  devise  a  series 

Lof  letters  known  as     Snellen's  test 
I  type,  that  are    used  in     connection 

Snellen's    Test-  with  the  test  case  in  measuring    the 

type. 

(Reduced).  vision.  They  consist  of  a  number  of 
letters  of  different  sizes,  which  at  different  dis- 
tances from  the  eye  are  so  constructed  as  to  form 

the  same  visual  angle.  The  letters  are  numbered 
from  two  hundred  feet  down  to  ten  feet,  showing 
us  how  far  the  separate  letters  should  be  read  with 
a  normal  eye. 


T  B 

D  L  N 

P  T  E  R 

r  z  B  s  B 

oai^  ZT  c 


33      REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

Q.     How  do  you  test  the  visual  acuteness? 

A.  A  Snellen  test  card  is  hung  in  a  well- 
lighted  room  at  a  distance  of  twenty  feet  from 
where  your  patient  sits,  and  each  eye  is  tested  sep- 
arately. With  a  shade  or  card  over  the  patient's 
left  eye,  you  ask  him  to  read  the  test-type  from  the 
large  letters  down  as  far  as  he  can  see.  Now,  if 
your  patient  can  see  the  line  that  should  be  read  by 
the  normal  eye  at  twenty  feet,  we  use  this  figure 
for  the  denominator  of  a  fraction,  and  we  find  that 
the  vision  in  the  right  eye  is  ||,  which  is  equal  to 
1,  or  normal  vision. 

Now,  with  the  right  eye  covered,  we  ask  him 
to  read  with  the  left  in  the  same  manner,  and  find 
that  at  this  distance  from  the  card,  thatis,  twenty 
feet,  he  can  only  read  as  far  down  as  the  line 
marked  forty  feet,  or  the  line  that  should  be  read 
by  the  normal  eye  at  a  distance  of  forty  feet.  Tak- 
ing this  number  for  the  denominator  of  a  fraction 
as  before,  we  find  that  the  vision  in  the  left  eye  is 

2  0 
TO-- 

Now,  supposing  he  could  only  read  at  twenty 
feet,  the  line  that  should  be  read  by  the  normal  eye 
at  200  feet,  then  we  would  express  his  vision  by  the 
fraction  ^^etc.  In  many  cases  you  will  find 
that  they  not  only  read  the  normal,  or  |4  line,  but 
they  can  do  better,  that  is,  they  can  read  at  twenty 


REFRACTION  AND  LENSES. 


33 


34       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

feet  the  line  that  by  the  normal  eye  is  only  sup- 
posed to  be  read  at  fifteen  or  twenty  feet,  as  the 
case  may  be,  and  in  the  same  way  using  this 
number  as  the  denominator,  we  have  the 
aeuteness  of  vision  expressed  by  the  fraction  20:15, 
or  20:10,  which  is  better  than  normal,  a  condition 
frequently  found  to  exist.  This,  then,  gives  us  the 
aeuteness  of  vision  for  distance  or  the  far  point 
(punctum  remotum,)  as  it  is  called;  Avhile  we  deter- 
mine the  aeuteness  of  vision  for  the  near  point 
(punctum  proximum)  by  the  use  of  small  type 
called  Jager  type,  numbered  1,  2  and  3,  and  the 
ability  to  read  this  type  without  the  use  of  convex 
glasses  gives  us  the  aeuteness  of  vision  for  the  near 
point  (punctum  proximum,)  and  the  difference  be- 
tween the  near  point  and  far  point  is  what  is 
known  as  the  "range  of  accommodation,"  also  call- 
ed the  power,  or  amplitude  of  accommodation. 

This  we  shall  consider  more  fully  in  a  separ- 
ate chapter. 


CHAPTER  III. 


Accommodation. 

"     Q.     What  is  meant  by  the  accommodation  of 
the  eye? 

A.  In  the  chapter  on  the  anatomy  of  the  eye, 
we  likened  it  to  a  camera  obscura,  and  like  a  cam- 
era, it  must  be  capable  of  adjusting  itself  for  im- 
ages at  different  distances.  Now,  with  a  camera, 
when  we  wish  to  get  a  focus  of  an  image,  or  pic- 
ture, at  some  distant  point,  we  must  shorten  up 
the  distance  from  the  lens  to  the  focus  glass,  which 
corresponds  to  the  sensitive  coat  of  the  eye,  or 
retina.  This  is  done,  as  you  all  know,  by  a  sliding 
adjustment  of  the  camera,  by  which  its  antro-pos- 
terior  diameter  is  either  increased  or  diminished, 
as  the  case  may  require.  This  is  very  necessary 
for  its  adaptation  to  different  distances,  as  in  all 
lenses  the  focal  point  becomes  farther  away  as  the 
object  is  brought  closer. 

Now,  the  eye-ball  being  incapable  of  chang- 
ing its  antro-posterior  diameter  on  account  of  its 

35 


36      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

inextensibility,  this  adjustment  must  take  place  in 
some  other  way,  and  we  find  that  this  is  accom- 
plished by  the  action  of  the  ciliary  muscle  on  the 
crystalline  lens.  This  lens,  as  we  have  seen,  is  a 
soft  body  inclosed  in  a  covering  called  the  capsule 
of  the  lens,  which  is  attached  to  the  suspensory 
ligament,  which  in  turn  is  attached  to  the  ciliary 
muscle.  By  the  action  of  this  muscle,  the  lens  is 
changed  so  as  to  make  it  more  convex,  thus  ena- 
bling the  image  coming  from  a  near  object  to  be 
properly  focused  at  the  "yellow  spot"  of  the  retina. 
This  change  takes  place  mostly  on  the  anterior  sur- 
face of  the  lens.  This  is  called  the  accommodation 
of  the  eye. 

Q;  Is  the  accommodation  of  the  eye  called 
into  frequent  use? 

A.  Yes;  every  time  the  eye  is  changed  from 
one  object  to  another  situated  at  different  dis- 
tances. 

Q.  Does  the  accommodative  power  of  the 
eye  differ  much  in  different  individuals? 

A.  In  all  persons  with  emmetropic,  or  nor- 
mal eyes,  it  is  nearly  the  same  at  the  same  age. 

Q.  What  does  punctum  remotum,  or  r,  mean 
in  connection  with  the  accommodation  of  the  eye? 


ACCOMMODATION.  37 

A.  It  means  the  farthest  point,  or  the  maxi- 
mum distance  of  vision  at  which  an  eye  can  see 
without  the  aid  of  glasses.  It  is  determined  by  the 
use  of  the  Snellen  test-type,  and  in  an  emmetropic, 
or  normal  eye,  it  is  at  twenty  feet,  or  infinity,  as 
rays  coming  from  this  distance  are  practically  par- 
allel. The  accommodation  is  supposed  to  be  en- 
tirely relaxed  and  the  eye  in  a  condition  of  mini- 
mum refraction. 

Q.  What  does  punctum  proximum,  or  p, 
mean? 

A.  It  means  the  nearest  point  at  which  fine 
print,  usually  Jager  No.  1,  can  be  seen  without  the 
aid  of  convex  glasses.  The  ciliary  muscles  are 
now  fully  contracted,  the  antro-posterior  diameter 
of  the  crystalline  lens  is  increased,  thus  increas- 
ing its  refractive  power,  it  bulges  forward  into 
the  anterior  chamber,  and  the  eye  is  in  its  maxi- 
mum condition  of  refraction. 

Q.  What  is  the  difference  between  the 
punctum  proximum,  or  p,  and  the  punctum  remo- 
tum,  orr,  called? 

A.  It  is  called  the  range  power,  or  amplitude 
of  the  accommodation,  and  is  determined  as  we 
have  seen  by  the  use  of  the  Snellen  type. 

Q.  Does  this  "range  of  accommodation" 
change  much  in  the  same  individual? 


38      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

A.  Yes,  very  much.  It  is  greatest  in  young 
life  and  gradually  diminishes  as  age  advances,  un- 
til the  73d  year  is  reached,  when  it  is  entirely  lost, 
and  the  punctum  proximum  and  the  punctum  re- 
motum  become  the  same. 

Q.  What  is  this  gradually  receding  near 
point  called? 

A.  It  is  called  presbyopia,  or  old  sight, 
which  generally  begins  to  manifest  itself  at  about 
the  40th  year  in  emmetropes,  sometimes  earlier  in 
hypermotropes,  and  always  later  in  myopes. 

Q.  When  the  near  point  is  closer  to  the  eye 
at  a  certain  age  than  is  usual,  what  does  it  indi- 
cate? 

A.     It  indicates  myopia. 

Q.  When  it  is  farther  away  than  usual,  what 
does  it  indicate? 

A.     It  indicates  hypermetropia. 

Q.  What  other  action  of  the  eye  is  intimately 
associated  with  the  act  of  accommodation? 

A.  The  act  of  converging  the  eyes,  or  the 
change  which  takes  place  in  the  position  of  the 
eye,  as  regards  their  axis  when  converging  them, 
so  as  to  look  from  a  distant  object  to  one  close  to 
the  eves. 


CHAPTER  IV. 


Emiuetropia  =  Em.     Hypermetropia  =-  H. 

Q.  What  name  is  given  to  that  condition  of 
the  eye  whose  refractive  conditions  most  closely 
resemble  a  perfect  optical  instrument? 

A.  Emmetropia,  which  is  defined  by  Landolt 
of  Paris,  to  be  one,  the  "retina  of  which  is  found  at 
the  principal  focus  of  its  dioptric  system;  or  one 
which  united  parallel  rays  on  its  retina,  or  ex- 
pressed in  another  manner,  the  punctum  remotum 
of  which  is  situated  at  infinity."  ' 

Q.  Is  this  condition  of  emmetropia  very  fre- 
quently found  to  exist? 

A.  The  examination  of  a  large  number  of 
eyes,  by  difi'erent  investigators,  shows  it  to  exist  in 
about  twenty  per  cent,  of  the  eyes  examined. 

Q.  How  are  rays  of  light  refiected  from  the 
retina  in  an  emmetropic  eye? 

A.  As  the  focal  point  for  rays  entering  the 
emmetropic  eye  is  at  the  principal  focal  point  of 

39 


40      REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

the  dioptric  media,  the  emergent  rays  are  parallel 
on  leaving  the  eye. 

Q.  Does  an  emmetropic  eye  require  the  aid 
of  a  glass  of  any  kind  to  see  distinctly? 

A.  No;  as  the  rays  are  parallel,  the  punctum 
remotum  is  at  infinity,  and  hence  will  not  require 
any  glass  for  distant  vision. 

Q.  Do  emmetropic  eyes  ever  undergo  any 
change  in  their  refraction? 

A.  Yes;  an  emmetropic  eye  may  become  my- 
opic from  the  conditions  giving  rise  to  myopia.  In 
fact,  some  writers  contend  that  emmetropia  is  only 

Figure  7. 


The  Emmetropic  Eye.     Parallel  rays  are  focused  on  the  retina. 
(After   Valk). 

a  stage,  or  point,  reached  in  the  refractive  condi- 
tions of  the  eye,  in  its  transition  from  hypermetro- 
pia  to  myopia.  It  is  a  fact,  however,  that  in  em- 
metropia we  have  not  only  the  best  optical  condi- 
tion to  be  found  in  the  eye,  but  we  have  also,  in  em- 


EMMETROPIA.     HYPERMETROPIA.  41 

metropia,  the  most  healthy  condition  of  the  media, 
membranes,  etc.,  and  also  an  eye  which  is  capable 
of  performing  the  greatest  amount  of  work  with- 
out giving  rise  to  asthenopia,  or  eye  strain,  and 
that  any  great  amount  of  deviation  from  this  con- 
dition of  refraction  is  generally  accompanied  with 
asthenopia.  There  are  several  reasons  justifying 
this  claim,  denied  by  many,  as  to  its  being  a  nor- 
mal eye.  It  is,  however,  a  good  standard  to  use  in 
estimating  refractive  errors,  and  it  is  likely  that 
for  this  reason,  if  for  no  other,  it  will  continue  to 
be  regarded  as  such.  Any  deviation  from  emme- 
tropia  is  called  ametropia,  of  which  hypermetro- 
pia,  myopia,  and  astigmatism  are  varieties. 

Q.     What  is  hypermetropia,  and  what  is  its 
principal  cause? 

Figure  8. 


The  Hypermetropic  Eye.     Parallel  rays  are  focused  behind  the 

retina.     (After  Valk). 

A.     Hypermetropia  is  that  condition  or  va- 
riety of  ametropia,  in  which  the  principal  focal 


42       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

point  of  the  dioptric  media,  tliat  is,  the  cornea, 
aqueous  humor,  crystalline  lens,  and  vitrious  hum- 
or, lie  behind  the  retina.  It  is  principally  caused 
by  the  visual  axis  of  the  eye  being  shorter  than  the 
focal  point  of  the  eye.  Some  claim  it  may  also  be 
caused  by  a  lack  of  density,  and  hence  refractive 
power  on  the  part  of  the  dioptric  media. 

Kays  of  light  reflected  from  the  retina  of  an 
hypermetropic  eye  are  divergent  after  leaving  it. 
This  condition  of  hypermetropia  is  also  called  far- 
sightedness. The  cause  of  hypermetropia  are 
nearly  always  congenital,  nearly  all  eyes  being 
hypermetropic  at  birth,  though  it  may  be  caused 
surgically  by  the  removal  of  the  crystalline  lens, 
as  in  operation  for  .cataract. 

Q.  What  are  the  symptoms  of  hypermetro- 
pia? 

A.  On  looking  at  small  objects,  like  fine 
print,  it  is  hard  to  maintain  distinct  vision  for  any 
length  of  time,  without  blurring,  and  persons  with 
hypermetropia  are  generally  looking  for  a  strong 
light  to  enable  them  to  see  more  distinctly,  and  we 
may  have  irritation  of  the  eye-lids,  or  even  inflam- 
mation, or  conjunctivitis,  following  the  persistent 
use  of  the  eyes  under  these  circumstances.  The 
pupil  is  apt  to  be  contracted  in  hypermetropia,  and 
looking  at  the  eye  closely  will  generally  reveal  a 


EMMETROPIA.     HYPERMETROPIA.  43 

shallow  anterior  chamber,  and  if  you  have  a  high 
degree,  you  can  generally  notice  that  the  eye  is 
much  smaller  than  normal,  giving  rise  to  a  short 
antro-posterior  diameter,  thus  causing  axial  hy- 
permetropia. 

The  glass  used  to  correct  this  condition  of  re- 
fraction, as  we  shall  see  later  on,  is  always  a  con- 
vex, or  plus,  glass;  as  the  action  of  this  glass  is  to 
converge  rays  of  light  to  a  point,  we  place  it  be- 
fore the  hypermetropic  eye,  and  by  assisting  the 
dioptric  media  of  the  eye  the  rays  are  brought  to 
a  focus  more  in  front  or  on  the  retina,  where  it 
should  be,  in  order  to  have  a  clear  and  distinct 
image. 

Q.  How  many  kinds  of  hypermetropia  as  re- 
gards its  aetiology,  or  cause,  are  there,  then? 

A.  Two  kinds;  first,  where  the  visual  axis  of 
the  eye  is  too  short,  which  is  called  axial  hyperme- 
tropia, and  second,  where  there  is  a  deficiency  in 
the  density  or  refractive  power  of  the  dioptric  me- 
dia, called  curvature  hypermetropia.  To  facilitate 
a  description  of  axial  hypermetropia,  it  is  divided 
into  three  varieties,  that  is,  manifest,  latent,  and 
total  hypermetropia.  These  varieties  can  best  be 
explained  by  citing  a  case  for  illustration:  A 
young  lady  twenty-four  years  old,  comes  com- 
plaining of  her  eyes.    She  has  difficulty  in  sewing 


44      REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

or  reading  for  any  length  of  time  without  causing 
strain  and  headache.  Her  vision  is  tested  in  the 
usual  manner  with  the  Snellen  test-type,  at  twen- 
ty feet,  and  we  find  that  she  can  read  down  to  the 
line  that  should  be  seen  by  the  emmetropic  eye  at 
twenty  feet,  so  using  this  figure  as  the  denomina- 
tor of  a  fraction,  we  have  her  vision  expressed  as 
f^  in  both  eyes.  Now,  b}'  taking  a  plus  glass  of 
ID.  and  placing  it  before  her  eye,  we  find  that  this 
will  not  give  her  increased  vision;  neither  will  it 
cause  any  blurring  of  her  vision  up  to  f  {J  Now 
this  ID.  convex  glass  represents  her  manifest  hy- 
permetropia,  but  as  this  does  not  correct  her  ame- 
tropia, or  relieve  her  asthenopia,  we  conclude  to 
paralyze  the  accommodation  by  the  use  of  a  solu- 
tion of  atropine,  say  four  grains  to  the  ounce,  a 
few  drops  instilled  three  times  a  day  for  a  period 
of .  three  days.  We  now  find  that  without  her 
glasses  her  vision  is  reduced  to  ^%\  ,  but  with  a 
-|-3  D.  lens,  her  vision  is  immediately  brought  up 
to|o,  or  normal.  Now  this  3  D.  represents  her 
total  hypermetropia,  and  the  difference  in  the 
glass  accepted  before  using  the  mydriatic,  and  the 
one  accepted  after  will  represent  the  amount  of 
latent  hypermetropia,  w^hich  in  this  case  is  repre- 
sented by  2D.  Now  in  this  case,  after  recovering 
from  the  use  of  the  atropine,  she  accepts  a  -^1.75, 
which  gives  her  |^  vision,  the  balance  of    1.25D. 


EMMETROPIA.      HYPERMETROPIA.  45 

will  be  taken  care  of  by  the  aeeonimodatlon  of  the 
eye. 

In  some  cases,  like  the  foregoing,  we  may 
have  what  is  called  a  spasm  of  the  accommodation, 
which  results  from  a  prolonged  effort  of  the  accom- 
modation in  trying  to  overcome  the  hypermetro- 
pia,  so  as  to  produce  distinct  vision  before  glasses 
are  prescribed,  and  in  these  cases  we  generally 
find  it  necessary  to  use  atropine  before  being  able 
to  relieve  our  patient  of  their  asthenopia. 

We  will  further  illustrate  the  different  varie- 
ties of  hypermetropia  by  selecting  a  few  represen- 
tative cases  from  our  note-book : 

First  case.  Manifest  Hypermetropia.  Boy 
eighteen  years  old,  complained  of  eyes  hurting  and. 
vision  blurring  when  he  would  use  his  eyes  for  any 
length  of  time.  On  taking  his  vision,  we  find  that 
with  the  O.  D.  V.  equals || .  (Opticum  dextrum, 
or  right  eye  vision);  and  that  of  O.  S.  V.  equals  || 
(Opticum  sinistrum,or  left  eye  vision).  Now  with  a 
-r-0.4SD.S.  the  vision  still  remains  f^},  but  the 
asthenopia,  or  eye  strain,  is  removed  by  his  wear- 
ing this  glass  all  the  time. 

Second  case.  Latent  Hypermetropia.  Young 
lady,  twenty  years  old,  complained  in  much  the 
same  way  when  using  her  eyes  for  study,  and  we 


46       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

find    that    her    vision  is    1^,   and  that    with    a 
-|-1.25  D.  S.  her  vision  is  brought  up    to    I? ,    but 
as  this  does  not  correct  her  eye  strain,  on  account 
of  her  inability  to  relax  her  accommodation,  we 
use  a  solution  of  atropine,  four  grains  to  the  ounce 
for  three  days,  and  we  now  find  her  vision  has 
gone  back  to  H,   but  with  a  -!-4D.  her  vision   is 
brought  up  to  U.     Now  this  additional  2.75  D. 
of  hypermetropia  brought  out  by  the  use  of  atro- 
pine, represented  concealed  or  latent  hypermetro- 
pia.   While  the  total  is  represented  by  the  4D., 
which  she  accepts  with  a  mydriatic.    It  is  very 
rarely  that  we  can  ever  correct  the  total  hyperme- 
tropia by  prescribing  glasses  for  full   correction 
without  causing  strain  of  the  accommodation  from 
the  opposite  direction,  and  we  must  always  leave 
from  1  to  1.50D.  uncorrected.    This,  however,  is  my 
custom,  and  it  seems  to  give  the  best  satisfaction. 
There  are  certain  cases,  for  example,  where  there 
is  interna]  strabismus,  or  squint,  accompanying  a 
high  degree  of  hypermetropia,  where  it  may  be  ne- 
cessary to  prescribe  full  correction  with  a  view  of 
overcoming  the  squint.    This  had  better  be  done  in 
connection  with  the  use  of  atropine,  as  in  this  way 
you  reduce  the  tendency  to  convergence  by  para- 
lyzing the  accommodation. 

It  may  be  best  to  add,  in  concluding  this  sub- 
ject of  hypermetropia,  that  in  order  to  get  perma- 


EMMETROPIA.     HYPERMETROPIA.  47 

nent  relief  from  the  eye  strain  resulting  from  it, 
that  it  will  be  necessary  to  wear  the  correcting 
o-l asses  all  the  time,  and  not  alone  for  close  work, 
as  many  seem  to  think  all  that  is  necessary.  It  is 
very  necessary  to  see  that  the  frames  fit  properly 
and  that  the  optical  centers  of  the  lens  correspond 
with  the  pupillary  distance  of  the  eyes,  as  all  de- 
centred  lenses  act  as  prisms,  and  may  thus,  uncon- 
sciously, produce  the  exact  condition  they  are  in- 
tended to  correct.  This  fact  it  is  always  best  to 
bear  in  mind  in  prescribing  glasses,  and  especially 
so,  if  the  amount  of  ametropia  be  very  great. 

Q.  Do  you  ever  meet  cases  of  hypermetropia 
in  which  the  patient  will  not  accept  a  convex  glass, 
that  is,  when  the  vision  is  already  1,1  and  where 
a  convex  glass  will  not  only  not  improve  vision, 
but  actually  bhir  it,  yet  3'ou  are  satisfied  from  the 
asthenopia  complained  of  and  as  the  result  of 
your  opthalmoscopic  and  retinosco})ic  examina- 
tion, that  your  patient  has  a  considerable  amount 
of  hypermetropia? 

A.  Yes;  such  cases  are  frequently  met  with, 
and  in  such  cases  all  the  hypermetropia  is  of  the 
latent,  or  concealed,  variety,  and  owing  to  the  con- 
dition of  the  accommodation,  which  has  become 
irritable  and  spasmodic,  such  cases  will  not  accept 
a  convex  glass  until  you  reduce  the  irritability  and 


48      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

spasm  of  the  accommodation  by  the  use  of  a  myd- 
riatic for  several  days,  when  you  will  find  you  can 
correct  all  of  the  latent  hypermetropia. 


CHAPTER  V. 


Myopia  =  M. 

Q.     What  is  myopia? 

Figure  9. 


Tiie  Myopic  Eye .     Parallel  rays  are  focused  before    reaching  the 
retina .     (After  Valk . ) 

A.  It  is  that  variety  of  ametropia,  in  which 
the  principal  focal  point  of  the  dioptric  media  lies 
anterior  to  the  retina,  and  in  which  only  those  rays 
that  came  from  a  nearer  point  than  twenty  feet,  or 
infinity,  can  be  brought  to  a  point  on  the  "yellow 
spot"  of  the  retina.  This  point  from  which  the 
rays  diverge  in  front  of  the  eye  is  the  punctum  re- 
motiim  of  the  eye,  and  all  rays  coming  from  objects 
between  this  punctum  remotum  and  the  eye  cau 

49 


50      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

be  seen  distinctly,  because  they  are  focused  on  the 
retina,  according  to  the  rule  that  the  nearer  the 
object  is  to  a  lens  the  longer  is  its  focal  distance 
and  vice  versa. 

Q.     How  many  kinds  of  myopia  have  we? 

A.  Two  kinds.  First,  the  axial  myopia  in 
which  the  axis  of  the  eye  is  longer  than  its  princi- 
pal focal  distance,  and  second,  curvature  myopia, 
in  which  the  fault  lies  in  the  dioptric  media,  that 
is,  possessing  too  great  refractive  power,  or  too 
great  a  curvature,  by  which  the  focus  for  parallel 
rays  are  brought  to  a  point  too  near  the  nodal- 
point  of  the  eye. 

Q.  Which  of  those  two  causes  is  the  princi- 
pal one  in  producing  myopia? 

A.  The  first,  or  the  axial  myopia,  is  supposed 
to  be  the  principal  cause.  The  curvature  myopia 
may  be  caused  by  disease  of  the  cornea  such  as 
conical  cornea,  or  any  other  condition  that  may 
increase  the  curvature,  and  hence  the  refraction 
of  the  cornea  or  lens. 

Q.  What  theories  are  advanced  as  to  the 
causes  which  result  in  conditions  which  lead  up  to 
the  development  of  myopia? 

A.  There  are  three  theories  as  to  the  cause 
of  myopia.    First,  the  anatomical  theory,  which 


MYOPIA.  51 

holds  that  the  primary  cause  is  to  be  found  in  the 
orbit,  which,  owing  to  its  peculiar  shape,  predis- 
poses to  the  elongation  of  the  ej^o-ball  and  thus  to 
Ihe  development  of  axial  myopia.  Second,  or  me- 
chanical theory,  ascribes  axial  myopia  to  the  com- 
pression of  the  eye  muscles  on  the  eye-ball,  thus 
producing  distention  of  the  ball  backwards. 

The  third,  or  inflammatory  theory,  is  held  by 
some  as  the  cause,  for  the  reason  that  myopia  is 
frequently  found  to  exist  in  connection  with  in- 
llammatory  conditions,  such  as  chroiditis,  sclero- 
tis,  etc.,  which  is  caused  by  obstructing  the  venous 
circulation  resulting  from  certain  habits  of  life, 
such  as  stooping,  or  bending  over  at  school  or 
working  where  the  illumination  is  insufficient  to 
see  without  extra  effort,  etc.  This,  however,  is  de- 
nied by  some,  as  only  a  very  small  per  cent,  of 
those  living  or  working  under  such  conditions,  are 
myopic.  It  is  more  frequently  seen  in  some  coun- 
tries than  others,  thus  in  Germany  it  is  much  more 
frequently  seen  than  in  the  United  States, 

Q.     What  are  the  indications  of  myopia? 

A.  They  are  both  objective  and  subjective. 
The  objective  being  a  large  prominent  eye-ball,  a 
dilated  pupil,  and  a  deep  anterior  chamber,  while 
the  subjective  indications  are  an  inability  to  see 
things  distinctly,  at  a  distance  everything  appear- 


52      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

ing  foggy  and  indistinct,  and  in  high  degrees  of 
myopia,  the  object  must  be  brought  close  to  the 
eye  to  see  it  clearly.  The  latter  condition  of  high 
myopia  is  also  frequently  combined  with  diver- 
gent strabismus,  or  a  turning  out  of  the  eyes,  in 
which  case  the  patient  usually  uses  one  eye  at  a 
time,  as  binocular  vision  is  impossible  under  these 
circumstances. 

Myopes  are  usually  more  given  to  close  work, 
such  as  reading  and  work  requiring  the  object  to 
be  brought  near  the  eyes.  They  are  not  given,  as 
a  rule,  to  sport  of  an  out-door  character,  on  ac- 
count, usuafly,  of  their  poor  visions.  Myopia  is 
very  apt  to  increase,  and  sometimes  it  produces 
such  change  in  the  fundus  as  to  very  seriously  im- 
pair the  eye-sight.  There  is,  in  some  cases  of  my- 
opia, a  drawing  away  of  the  retina  from  the  chor- 
oid, about  the  edge  of  the  optic  disk.  This  is  gen- 
erally semi-lunar  in  shape,  and  is  called  posterior 
staphyloma.  This  may  extend  to  the  extent  of 
causing  a  detachment  of  the  retina,  and  more  or 
less  loss  of  sight. 

There  is  one  other  peculiarity  about  the  myo- 
pic eye,  and  that  is  the  feeble  development  of  the 
ciliary  muscle.    The  far  point  of  the  myopic  eye  is 
"SO  near  to  the  eye,  that  the  accommodation  is  very 
little  employed,  and  as  a  result  of  this  non-use,  the 


MYOPIA.  '  53 

ciliary  muscle  is  never  very  fully  developed,  hence 
it  is  rarely  ever  necessary  for  us  to  use  a  mydriatic 
in  myopes,  unless  we  suspect  artificial,  or  spuri- 
ous, myopia,  the  result  of  tonic  spasm  of  the  ciliary 
muscle. 

Q.  Is  there  any  compensating  feature  about 
myopia  at  all? 

A.  The  only  possible  one  that  it  is  known  to 
possess  is  the  well-known  fact  that  it  delays  pres- 
byopia, if  it  does  not  entirely  do  away  with  the  ne- 
cessity of  wearing  glasses  for  this  condition, 
which,  as  we  shall  see,  in  emmetropia  and  hyper- 
metropia,  shows  itself  at  about  the  40th  year, 
when  it  is  necessary  for  us  to  use  a  convex  glass 
before  the  eye  to  restore  the  gradually  receding 
near  point  to  a  position  that  enables  us  to  work  at 
close  work  without  straining  the  eyes. 

Q.  How  do  you  proceed  to  correct  myopia 
with  lenses? 

A.  Well,  we-,  have  seen,  when  speaking  of 
concave  lenses,  that  their  action  causes  a  di- 
vergency of  the  rajB  of  light  passing 
through  them.  Now  in  myopia,  we  find  that  the 
rays  coming  from  the  myopic  eye  are  converged  to 
a  point  in  front  of  the  eye,  so  we  wish  to  change 
their  course  so  as  to  produce  a  parallelism  of  the 


54     REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

rays,  for  we  have  also  seen  that  as  the  rays  pass 
from  the  eye,  so  also  do  they  pass  into  the  eye. 
If  the  rays  be  made  to  pass  out  of  the  eye  in 
parallel  lines  by  the  diverging  action  of  concave 
glasses,  so  also  will  rays  coming  from  infinity  pass 
in  in  parallel  lines,  thus  producing  distinct  vision 
for  distance,  or  infinity,  and  the  weakest  concave 
glass  that  produces  this  condition,  is  the  one  to 
prescribe  for  constant  wear,  and  it  should  be  worn 
as  close  to  the  cornea  of  the  eye  as  possible,  and 
this  glass  will  usually  suffice  for  all  purposes,  un- 
less the  myopia  be  of  a  high  degree,  when  it  will 
be  necessary  to  give  a  lens  somewhat  weaker  than 
this  for  close  work. 

We  shall  speak  of  this  more  fully  under  the 
head  of  presbyopia.  We  will  now  bring  this  chap- 
ter on  myopia  to  a  close  by  citing  a  few  typical 
cases  as  taken  from  our  note-book.  Of  course,  in 
getting  at  the  acuteness  of  vision,  we  resort  to  the 
•same  method  as  in  hypermetropia.  We  have  a  pati- 
ent sit  at  a  distance  of  20  feet  from  the  Snellen 
test-type,  in  a  well-lighted  room,  and  each  eye  is 
measured  separately,  while  a  shade  or  cover  is 
held  over  the  other,  and  a  note  is  made  of  the  vis- 
ion of  each  eye  in  the  proper  manner..  You  will 
find  that  in  cases  of  myopia  that  if  you  place  a  con- 
vex lens  before  the  eye,  the  vision  is  made  worse, 


MYOPIA.  55 

at  once  leading  you  to  suspect  the  existence  of  my- 
opia, which  you  proceed  to  prove  by  the  use  of 
concave  glasses,  the  ophthalmoscope,  and  retiuo- 
scope. 

First  case.    Simple  Myopia.    Mrs.  S.,  age  33. 
O.  D.  V.  equals  fH,  with  a  —3  D.  S.  equals  |M- 
O.  S.  V.  equals  f^,  with  a  —3  D.  S.  equals  -{J  -|- 
This    case  read    in    the    following  manner: 
Right  eye  vision,  without  glasses,  equals  twenty- 
fiftieths;  that  is,  she  could  only  see  at  twenty  feet 
the  line  that  should  be  seen  by  the  emmetropic  eye 
at  fifty  feet,  but  by  placing  a  minus  glass  before 
her  eyes,  her  vision  is  brought  up  to  twenty -twen- 
tieths plus,  which  means  a  little  better  than  nor- 
mal.   In  the  left  eye  we  find  the  same  condition  of 
affairs,  and  with  the  same  glass  she  gets  the  same 
improvement;  hence  you  see  this  is  a  case  of  sim- 
ple myopia,  or  short-sightedness,  as  it  is  called. 

The  next  case  is  a  case  in  which  there  is  a  dif- 
ference in  the  amount  of  ametropia  in  each  eye,  a 
condition  called  anisometropia. 

Second  case.    Myopia.    Mr.  H.  G.,  age  53  years. 

O.  D.  V.  A"o  w  -  5.50  D.  S.  =  H- 
O.  S.  V.  ^Vo  —  w  —  6.50  D.  S.  =  U- 

Now,  in  this  case,  we  find  vision  very  much  re- 
duced without  glasses,  but  with  a  — 5.50  D.  S.  over 


56      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

the  right  eye,  vision  was  increased  to  |^,  and  with 
a  — 6.50  D.  S.  over  the  left  eye,  vision  was  made 
only  II -J-.  The  ophthalmoscope  did  not  show  any 
pathological,  or  decreased  condition  of  the  eye,  as 
we  ought  reasonably  to  expect,  and  his  poor  vision 
can  only  be  ascribed  to  the  fact  that  he  did  not 
wear  glasses  until  the  last  few  years,  which  I  think 
often  produces  some  change  in  the  retinal  nerve 
elements,  thus  rendering  normal  vision  impossible. 

This  man  was  able  to  use  these  glasses  for  both 
near  and  far  work,  thus  partly  compensating  him 
for  his  myopia  in  not  being  obliged  to  use  a  convex 
glass  for  close  work  only.  In  the  above  case,  the 
difference  in  the  correcting  glass  constitutes,  as 
we  have  said,  anisometropia. 

In  the  last  case  just  cited,  we  find  that  it  re- 
quires a  — 5.50  D.,  or  about  a  7  inch  glass  to  render 
the  converging  rays  of  this  myopic  eye  parallel. 
Now,  as  this  distance,  that  is,  7  inches,  is  the  far 
point  of  his  eye,  everything  beyond  this  point  will 
appear  indistinct  and  hazy.  We  are  thus  enabled 
to  get  some  idea  of  the  amount  of  myopia  in  a  given 
case,  by  having  them  hold  some  ordinary  type  as 
far  from  the  eye,  or  at  the  punctum  remotum,  as 
they  can  see  it  distinctly.  As  this  point  will  repre- 
sent the  focal  point  of  the  correcting  glass,  it  will 
give  us  some  idea  of  the  glass  required.    We  must 


MYOPIA,  67 

also  remember  that  concave  lens  have  a  negative 
focal  point,  and  instead  of  estimating  the  focal 
point  behind,  the  glass  when  applied  to  the  eye, 
you  must  calculate  the  focal  distance  in  front,  and 
accordingly  in  the  above  case,  we  find  this  to  be  7 
inches  in  the  right  eye  and  G  inches  in  the  left,  be- 
cause with  the  negative  focal  point  of  the  concave 
correcting  lens,  at  these  respective  points,  the 
rays  are  rendered  parallel,  and  distinct  vision  for 
distance  is  rendered  possible. 

There  are  a  few  cases  of  myopia,  generally  in 
the  aged,  which  is  caused  by  the  swelling  of  the 
crystalline  lens,  the  result  of  inflammatory  action 
in  the  lens  substance,  as,  for  example,  such  as  oc- 
curs in  senile  cataract.  The  effect  of  this  swelling 
is  to  increase  the  antro-posterior  diameter  of  the 
lens,  and  hence  its  refractive  power,  thus  produc- 
ing a  myopia  by  bringing  the  focal  point  in  front 
of  the  retina.  In  these  cases,  the  patients  are 
sometimes  able  to  read  without  the  use  of  glasses, 
where  previously  glasses  were  necessary.  This  is 
what  they  call  their  second  sight,  and  they  are  apt 
to  speak  boastingly  of  their  new  possession,  little 
dreaming  that  it  is  the  initial  stage  of  a  condition 
which  when  further  advanced  may  rob  them  of 
their  precious  sight  entirely. 


CHAPTER  VI. 


Astigmatisui  =  As. 

Q.     What  is  astigmatism? 

A.  It  is  that  condition  of  refraction  in  which 
rays  of  light  coming  from  a  given  point,  are  not 
all  brought  to  a  focus  at  the  same  place  on  the  ret- 
ina. 

Q.  HoTv  many  kinds  of  astigmatism  are 
there? 

A.  There  are  two  kinds;  regular  astigma- 
tism, and  irregular  astigmatism. 

Q.  What  is  the  cause  of  regular  astigma- 
tism? 

A.  A  difference  in  the  curvature  of  the  differ- 
ent meridians,  of  the  cornea,  or  lens. 

Q.  Where  is  it  most  frequently  found  to  be 
located? 

A.     In  the  cornea  of  the  eye. 

Q.  What  is  irregular  astigmatism,  and  what 
is  its  principal  cause? 

A.    It  is  a  difference  in  the  curvature  of  the 

58 


ASTIGMA  TISM.  59 

cornea  aud  leus,  the  same  as  regular  astigmatism, 
but  generally  tlie  result  of  traumatism,  disease, 
or  following  a  surgical  operation  on  the  eye. 

Q.  How  many  yarieties  of  regular  astigma- 
tism haye  we? 

A.     We  haye  flye  different  yarieties. 
Q.     What  are  their  different  names? 

A.  1st.  Simple  Hypermetropic  Astigmatism. 
(All.)  In  this  form  one  of  the  meridians  of  the  eye 
is  emmetropic,  usually  the  yertical,  while  the  mer- 
idian at  right  angles,  usually  the  horizontal,  is 
hypermetropic. 

2d.  Simple  Myopic  Astigmatism.  (Am.)  In 
this  form  one  of  the  meridians  of  the  eye  is  emme- 
tropic, usually  the  horizontal,  while  the  other  mer- 
idian, usually  at  right  angles,  that  is,  the  yertical 
meridian,  is  myopic. 

3d.  Compound  Hypermetropic  Astigmatism. 
(*H.  Ah.)  In  this  form  of  astigmatism,  both  merid- 
ians of  the  eye  are  hypermetropic,  but  one  more 
hypermetropic  than  the  other,  usually  the  horizon- 
tal. 

4th.  Compound  Myopic  Astigmatism.  (M.  Am.) 
In  this  form  of  astigmatism  both  the  meridians  are 
myopic,  but  one  meridian  is  more  myopic  than  the 
orher  usually  the  yertical. 


60      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

5th.  Mixed  Astigmatism.  (A.  hm.  or  A.  mil.) 
Tiiis  is  a  condition  of  refraction  in  which  one  mer- 
idian is  hypermetropic  and  the  other  meridian  my- 
opic. 

Q.    Is  astigmatism  frequently  found  to  exist? 

A.  Yes;  it  is  perhaps  the  most  frequent  form 
of  refractive  error,  as  well  as  the  most  frequent 
source  of  asthenopia,  or  eye-strain. 

Q.  What  variety  is  most  frequently  met 
with? 

A.  Simple  hypermetropic  astigmatism,  with 
compound  hypermetropic  astigmatism  a  close  sec- 
ond. 

Q.  What  kind  of  lens  is  always  used  in  cor- 
recting astigmatism? 

A.  Cylindric  lenses  are  always  uses  to  correct 
astigmatism,  but,  of  course,  they  are  used  in  com- 
bination with  the  sphericals  in  cases  of  compound 
astigmatism. 

Q.  Should  cylindric  correcting  lenses  for  as- 
tigmatism be  worn  for  certain  work,  or  at  certain 
times  ? 

A.  No;  they  should  be  worn  for  all  kinds  of 
work,  and  at  all  times.  That  is,  they  are  for  con- 
stant wear. 


ASTIGMATISM.  61 

Q.  How  do  you  determine  the  i)resence  of  as- 
tigmatism? 

A.  There  are  several  methods  that  may  be 
named  in  the  following  order:  Snellen  test-type 
for  distance,,  the  astigmatic  chart,  the  ophthalmos- 
cope, the  shadow  test,  skioscopy,  or  retinoscopy, 
as  it  is  called,  Placidos  keratoscoi3e,  and  lastly,  by 
means  of  the  Javal  ophthalmometer. 

Q.  Describe  the  method  with  Snellen  test- 
type? 

A.  The  patient  is  seated,  as  before,  at  a  dis- 
tance of  twenty  feet  from  the  letters,  and  the  vis- 
ion tested  in  the  usual  manner.  We  will  find  the 
vision  as  a  rule,  below  fo  though  it  may  be 
normal,  and  the  patient  still  have  astigmatism. 
We  first  try  a  spherical  convex  lens,  and  we  find 
we  do  not  improve  the  sight  any.  We  next  try  a 
spherical  concave  with  the  same  result.  We 
should  remember,  to  begin  with,  rather  weak 
sphericals.  Now,  we  will  take  a  convex  cylinder 
and  placing  it  before  the  eye,  we  turn  it  in  the  cell 
of  the  trial  frame,  until  the  patient  says  he  can  see 
clearer  and  better.  We  keep  increasing  or 
decreasing  the  strength  of  the  cylinder  until  the 
very  best  visional  results  are  obtained,  always  re- 
membering to  place  the  axis  of  the  cylinder  at  the 
point  of  clearest  vision,  and  this  i)oint  will  be  in- 


62      REFRACTIVE  AXD  OPHTHALMIC  CATECHISM. 

dicated  in  degrees  by  the  figures  marked  on  the 
trial  frame.  For  example,  vre  find  that  our  pa- 
tient has  ^  vision  in  both  eyes,  and  with  eith- 
er a  convex  or  concave  spherical,  which  we  would 
naturally  try  first,  vision  is  not  improved.  Then, 
of  course  we  would  try  a  cylindric  lens,  taking 
first  a  convex  of  ID.  and  setting  it  in  the  trial 
frame  over  the  right  eye — the  left  being  covered 
as  usual — with  its  axis  at  180°,  slowly  turning  it 
from  left  to  right  until  a  point  is  reached  when  the 
patient  will  be  able  to  see  better,  and  we  note  this 
point  on  the  trial  frame,  which  in  this  case  we  will 
say,  is  at  90°.  Xow  we  take  a  still  stronger  lens, 
say  a  -r-1.25,  and  vision  is  made  |^-|-,  but  to  be  sure 
we  try  a  still  stronger  one,  say  a  -f -1.50  D.,  but  this 
causes  a  blur,  so  we  go  back  to  our  second  lens,  or 
►T-1-25  D.  cylinder,  and  we  find  this  gives  us  the 
best  result,  so  we  have  the  vision  of  this  eye  cor- 
rected as  follows : 

E.  E.  V.  fl  w  -I-  1.25  D.  Cyl.  Ax.  90°  =  M  -|-- 

which  reads  as  follows :  Eight  eye  vision  H  with  a 
plus  one  and  a  quarter  dioptric  cylinder  axis  at 
ninety,  vision  equals  twenty-twentieths  plus.  For 
the  sake  of  brevity,  we  will  say  that  we  find  the 
left  eye  vision  the  same,  and  that  it  is  corrected  by 
the  same  cvlinder  lens. 


ASTIG3IATISM. 


63 


Q.     What  is  the  astigmatic  chart,and  how  is  it 
used  to  determine  the  presence  of  astigmatism? 
Figure  10. 


Green's  Astigmatic  Chart. 

A.  The  astigmatic  chart,  of  which  there  are 
many  varieties,  is  a  chart  numbered  like  the  dial  of 
a  clock  with  the  numbers  from  1  to  12  in  the  same 
relative  position.  From  the  center  of  the  chart  to 
the  numbers  on  the  periphery  radiate  lines,  gen- 
erally three  in  number,  thus  forming  three  black 
lines  and  two  white  spaces.  The  back-ground  of 
the  chart  is  white,  so  the  contrast  is  well  marked. 
This  chart  is  hung  in  a  well-lighted  room,  say  10  ft. 
from  our  patient,  and  on  about  a  level  with  the 
eyes.  When  an  astigmatic  patient  looks  at 
the  lines  he  will  be  able  to  see  the  lines  in  one  mer- 
idian much  clearer  than  those  in  the  meridian  at 
right  angles  to  this;  for  example,  in  the  case  just 


64      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

cited,  the  patient  would  be  able  to  see  tlie  lines 
running  in  the  horizontal  meridian  much  better 
and  clearer  than  in  the  vertical,  while  in  the  ver- 
tical meridian  he  might  not  be  able  to  distinguish 
the  lines  and  spaces. 

Xow  the  cylinder  lens  with  its  axis  at  right 
angles  to  the  meridian  in  which  the  lines  are  seen 
most  distinctly,  that  will  bring  the  vertical  merid- 
ian out  clear  and  distinct,  will  represent  your  cor- 
recting cylinder  glass,  as  we  find  1.25D.  to  do  in 
the  above  case. 

The  method  of  determining  astigmatism  by 
the  use  of  the  ophthalmoscope,  retinoscope,and  ob- 
thalmometer,  will  be  considered  under  separate 
chapters.  The  keratoscope  is  an  instrument  in- 
vented by  Placido  of  Porto,  and  named  for  him.  It 
is  a  disk  about  8  or  9  inches  in  diameter  with  a  hole 
in  the  center;  on  the  surface  of  the  disk  is  a  series 
of  concentric  circles  in  black  and  white.  In  using 
it  the  patient  is  placed  with  his  back  to  the  light, 
and  by  holding  this  before  the  eye  and  looking 
through  the  aperture,  a  reflection  of  the  circles  is 
seen  on  the  cornea.  If  there  be  no  astigmatism 
the  circles  will  have  a  regular  shape  as  seen  on  the 
disk,  but  if  there  be  astigmatism,  they  will  appear 
oval  and  irregular  with  the  shortest  diameter  of 
the  oval  corresponding  to  the  meridian  v\'hich  is 
the  seat  of  the  astigmatism. 


ASTIGMATISM. 
Figure  11. 


65 


Placido's  Disk  or  Keratoscope, 

Q.  What  is  the  stenopaeic  slit,  and  for  what 
puri^ose  is  it  used? 

A.  It  is  a  metal  disk,  usually  found  in  a 
test  case,  and  is  made  to  fit  the  trial  frame. 
It    has    a    slit    about    1     inch    long     and    very 


66      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

narrow.  It  is  used  to  test  the  vision  in  the  various 
meridians  separately,  to  confirm  the  diagnosis  of 
astigmatism.  In  the  above  case,  which  we  will 
take  to  illustrate  the  use  of  the  stenopaeic  slit  also, 
we  would  put  it  before  the  eye  with  the  slit  in  the 
vertical  direction,  and  we  find  our  patient  has  vis- 
ion in  this  meridian  of  |f.  We  now  turn  it  so 
as  to  bring  the  slit  in  the  horizontal  meridian,  and 
we  find  that  he  can  only  see  as  far  down  as  the 
t^  line.  Xow,  by  taking  a  spherical  glass  and 
placing  it  before  the  eye,  this  spherical  will  act 
like  a  cylinder  with  the  stenopaeic  disk  over  the 
eye.  As  rays  of  light  are  only  admitted  in  the 
meridian  in  which  the  slit  is  placed,  as  all  the 
other  rays  are  cut  off  by  the  disk,  we  find  that  it  re- 
quires a  1.25  D.  S.  convex  to  bring  the  vision  up  to 
1^,  or  normal,  and  this  will  represent  the  num- 
ber of  the  cylinder  lens,  necessary  to  correct  the 
astigmatism  with  its  axis  at  right  angles,  or  at 
90°. 

In  using  the  slit  in  cases  of  compound  astig- 
matism, either  of  the  hypermetropic  or  myopic  va- 
riety, each  of  the  two  principal  meridians  must  be 
tested  separately,  and  the  difference  in  the  two 
will  represent  the  amount  of  astigmatism.  It  is 
unnecessary  to  add  that  we  do  not  rely  on  the  find- 
ing of  the  stenoaepic  slit  alone,  but  it  will  prove  a 


ASTIGjIaTISJ^I.  67 

good  corroborating  test  in  ^erv  many  cases  of  as- 
tigmatism. 

Q.  Tlius  far  we  have  only  spoken  of  the  first 
variety  of  astigmatism,  tliat  is,  simple  hyperme- 
tropic astigmatism.  Now  how  would  we  proceed  to 
use  these  various  tests  in  a  case  of  the  second  va- 
riety; namely,  compound  hypermetropic  astigma- 
tism? 

A.  Well, in  a  ease  of  compound  hypermetropic 
astigmatism,  we  have  a  case  of  simple  hypermetro- 
pia  combined  with  simple  hypermetropic  astigma- 
tism. In  that  case,  we  would  proceed  to  deal  with 
the  hypermetropia  alone  first,  and  bring  the  pa- 
tient's vision  up  to  the  highest  point  by  the  use  of 
a  convex  spherical  lens.  When  we  could  get  no 
further  improvement  with  sphericals,  we  take  and 
set  this  lens  in  the  back  cell  of  the  trial  frame,  and 
proceed  to  apply  cylinder  glasses  over  it,  trying 
the  different  numbers,  and  turning  it  to  different 
points,  until  the  best  possible  results  are  attained, 
and  the  very  best  vision  results.  This,  of  course, 
is  the  test  with  the  Snellen  type,  and  to  make  it 
more  clear  we  will  cite  another  case  from  our  note- 
book which  is  a  very  well  marked  case  of  this  var- 
iety of  refractive  error. 

Miss  M.  R.,  age  15  years,  was  sent  to  me  by  her 
teacher,  for  me  to  correct  her  vision.  She  could  not 


68       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

see  the  blaekbroad  even  when  in  a  front  seat,  and 
the  iTse  of  her  eves  was  accompanied  with  severe 
strain  and  blurring.  She  also  had  blepharitis,  or 
inflammation  of  the  edge  of  the  lids,  with  the  for- 
mation of  crusts  on  them.  The  Snellen  test  type 
gave  her  vision  in  each  eye  without  glasses  as 
-f^-^.  Now  in  the  usual  way,  I  applied  convex 
spherical  lens,  but  I  was  only  able  to  bring  her  vis- 
ion up  to  II  by  the  use  of  spherigals  alone,  and 
this  proved  to  be  one  of  4. SOD.  I  then  placed  this 
in  the  back  cell  of  the  trial  frame,  and  began  the 
use  of  convex  cylinders,  and  I  found  that  with  a 
convex  cylinder  of  2D.  with  its  axis  90  deg.,  her 
vision  became  ||.  The  left  eye  showed  exact- 
ly the  same  results,  and  the  other  different  tests 
confirmed  the  result.  So,  I  order  for  her  constant 
use  the  following  glasses,  which  she  wears  with 
great  satisfaction  and  comfort: 

K.  E.  Y.  =  oW  w  -1-  4.50  D.  S.  C  -I-  2  D.  cyl. 

ax.  90°  =  1^. 

L.  E.  V.  =  3^V  ^  -I-  4.50  D.  S.  C  -I-  2  D.  cyl. 
ax.  90°  =  f^ 

You  are  already  familiar  with  the  interpreta- 
tion of  these  formulae,  so  we  will  not  trouble  you 
any  more  with  it.  This,  then,  is  a  typical  case  of  the 
compound  hypermetropic  variety  of  astigmatism, 
so  we  shall  next  proceed  to  the  consideration  of 


ASTIGMATISM.  69 

the  third  variety,  that  of  simple  myopic  astigma- 
tism. Now  with  the  Snellen  type,  you  find  vision 
generally  reduced,  though  in  low  degrees,  it  need 
not  be  but  very  little  below  normal.  You  find  that 
spherical  glasses  do  not  improve  it,  so  you  try  the 
cylinders,  of  course,  and  you  find  that  on  turning 
the  glass  so  as  to  bring  the  axis  of  the  glass  into 
the  180  deg.  meridian,  that  vision  is  better,  the 
lines  which  before  were  plainer  in  the  vertical 
meridian  of  the  astigmatic  chart  are  now  all  equal- 
ly distinct,  and  you  can  if  you  are  not  satisfied,  try 
the  other  tests,  but  you  will  soon  learn  to  rely 
more  on  the  testing  case  than  on  any  other  single 
test. We  make  a  note  of  what  we  have  found, 
and  express  it  in  the  following  formulae: 

R.  E.  V.  =  H  w  —  .55  D.  cyl.  ax.  180°  =  ||. 

L.  E.  V.  =  H  w  —  .  55  D .  cyl.  ax.  180°  =  U- 

This  shows  us  then  a  case  of  simple 
mj'opic  astigmatism,  ''according  to  the  rule,-'  that 
is,  the  axis  of  the  cylinder  is  at  180°,  which  is  most 
generally  the  case,  but  if  it  were  at  90°  instead,  it 
would  be  said  to  be  "contrary  to  the  rule,''  but  you 
must  remember  that  in  hypermetropic  astigma- 
tism it  is  ''according  to  the  rule''  at  90°,  and  ''con- 
trary to  the  rule"  atl80o.  You  will  observe  that  in 
these  cases  of  simple  astigmatism,  either  hyperme- 
tropic or  myopic,  one  of  the  meridians  of  the  eye  is 


70      REFRACTIVE  A^D  OPHTHALMIC  CATECHISM 

eiiiiiietropic,  aud  the  other  ametropie,  and  that  it 
is  only  necessary  to  correct  but  one  meridian,  aud 
as  light  is  oulv  refracted  in  one  meridian  by  cylin- 
dric  glasses,  you  will  readily  appreciate  why  cylin- 
ders are  always  used  in  astigmatism. 

The  determination  of  the  fourth  variety,  that 
is,  compound  myopic  astig-matism,  is  the  same  in 
every  respect  as  that  of  compound  hypermetropic 
astigmatism,  except  in  the  use  of  concave  spheri- 
cals  aud  cylinder  lens  instead  of  the  convex.  You 
will  notice  that  the  vision  according  to  the  Snellen 
type  is  generally  lower  in  myopic  than  in  hyperme- 
tropic cases,  except  in  cases  of  very  high  degree  of 
hypermetropia;  but,  as  a  rule,  you  may  suspect 
myopia  first,  unless  you  have  good  proof  to  the 
contrary,  when  you  meet  a  patient  whose  vision  is 
very  much  reduced,  say  y-Trrr,  or  even  lower.  We 
will  likewise  select  a  case  of  compound  myopic  as- 
tigmatism from  our  case  book,  to  better  illustrate 
the  method  of  correcting  this  form  of  refractive 
error,  and  in  selecting  these  cases  you  will  observe 
that  I  select  only  those  of  rather  high  degree.  I 
do  this  to  make  the  case  more  clear  to  your  mind, 
but  you  must  not  conclude  from  this  that  all  the 
cases  you  meet  will  be  so  well-marked,  for  the  fact 
of  the  matter  is,  the  cases  of  low  degree  of  trouble 
are  the  ones  that  will  require  your  greatest  skill, 
as  well  as  the  ones  that  will  cause  your  patients, 


ASTIGMATISM.  71 

mauT  times,  the  greatest  amount  of  eye  strain. 
In  this  ease  of  compound  myopic  astigmatism, 
Mr.  C,  age  23  years,  of  literary  habits,  consulted 
me  in  regard  to  his  eyes,  which  were  giving  him 
considerable  trouble.  He  had  more  or  less  inflam- 
mation about  the  lids,  with  blepharitis,  and  being 
of  a  very  nervous  temperament,  felt  that  it  was 
largely  the  result  of  his  eye  trouble.  He  had  been 
wearing  a  pair  of  -3D.,  but  did  not  feel  that  they 
were  just  what  he  should  have.  In  examining 
each  eye  separately  by  the  Snellen  test-type,  vision 
was  found  to  be  t^  in  both  eyes.  Xow  with  the 
— 3D.  he  could  see  down  to  the  |^  line,  but  things 
did  not  look  distinct,  and  the  lines  of  the  astigma- 
tic chart  were  not  the  same,  that  is,  the  lines  in  the 
vertical  meridian  were  much  darker  and  clearer, 
so  trying  the  concave  cylinder  lenses,  I  found  that 
with  a  — 3.25D.S.  in  the  posterior  cell  of  the  trial 
frame,  and  with  a  — l,2oD.  cyl.  with  its  axis  at 
180°,  the  lines  on  the  chart  were  all  alike,  and  not 
only  this,  but  that  the  acuteness  of  vision  was 
brought  up  to  tl?  or  better  than  normal. 
With  the  left  eye,  by  the  same  manner,  I  found  that 
t7  vision  was  obtained  by  a  — 4D.S,  behind,  and  a 
— ID.  cyl,  axis  180°  in  front,  and  as  any  weaker 
spherical  would  reduce  the  acuteness  of  vision,this 
combination  was  ordered  for  constant  wear  with 
perfect  result: 


72       REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

E.  E.  Y.  =  i^  w  —  3.25  D.  S.  C  —  1.25  cyl.  ax. 
180«  =  Yh 

L.  E.  y.  =  !-«  w  —  4.00  D.  S.  C  —  1.00  D.  cyl. 
ax.  180°  —  -f-f . 

You  must  always  remember  to  give  the  weak- 
est concaye  spherical  lens  consistent  with  good 
vision,  and  as  there  is  always  some  danger  of  over- 
correcting  the  myopia,  I  make  a  practice  of  placing 
A-f-  spherical  of  .55D.  before  the  correcting  combi- 
nation, and  note  the  result.  If  they  can  see  just  as 
well  at  a  distance,  I  then  reduce  the  concave 
spherical  a  half  dioptre.  This  I  have  found  to  be 
good  practice,  but  I  always  correct  all  the  astig- 
matism I  can  find,  either  hypermetropic  or  myopic. 

Y'our  patient  may  have  some  trouble  in  get- 
ting used  to  them,  especially  if  there  be  much  as- 
tigmatism, on  account  of  the  distortion  of  objects, 
but  this  will  soon  pass  away,  if  you  can  persuade 
them  that  it  is  not  going  to  ruin  their  eyes,  as  some 
of  them  think.  I  find  it  a  good  practice  to  tell  them 
beforehand  that  the  glasses  will  make  things  look 
queer  and  out  of  shape  for  a  while,  but  that  it  will' 
all  pass  away  in  a  week  or  ten  days.  This  little 
explanation  beforehand  may  save  you  considera- 
ble subsequent  trouble,  as  I  find  few  patients  that 
can  wear  strong  minus  combination  without 
some  trouble  of  this  kind,  and  some  of  them   are 


ASTIGMATISM.  73 

not  always  ready  to  accept  your  explanation,  com- 
ing some  time  after  they  have  worn  the  glasses,  so 
it  is  always  better  to  forestall  this  by  explaining 
it  to  them  at  the  time. 

The  fifth  and  last  variety  of  astigmatism  is 
that  which  is  knoAvn  as  mixed  astigmatism.  In 
this  form  of  astigmatism  we  have  one  meridian, 
generally  the  horizontal  hypermetropic,  while 
the  meridian  at  right  angles  to  this,  generally  the 
vertical,  is  myopic.  This  is  a  class  of  cases  which 
fortunately  is  not  very  frequently  met  with,  and  in 
something  like  three  thousand  cases  of  refraction, 
I  do  not  remember  to  have  met  it  a  dozen  times. 
Now  as  one  meridian  is  myopic,  and  the  other  hy- 
permetropic, your  first  conclusion  would  be  to  cor- 
rect each  meridian  with  its  proper  cylinder,  that 
is,  the  hypermetropic  meridian,  with  a  plus  cylin- 
der at  90*^,  and  a  myopic  with  a  minus  cylinder  at 
180°.  This  is  what  is  called  a  cross  cylinder,  and 
you  can  correct  this  class  of  cases  very  well  in  this 
way,  but  the  cross  cylinder  is  an  expensive  combi- 
nation, so  this  must  always  be  a  consideration,  and 
instead  of  it  we  generally  use  a  concave  spherical 
combined  with  a  convex  cylinder,  which,  as  you 
will  see,  sives  us  the  same  result. 


>  t?' 


I  shall  select  a  case  from  my  note-book  to  il- 
lustrate this  also.    F.  S.,  age  10  years,  is  found  by 


74      REERACTIVE  AND  OPHTHALMIC  CATECHISM. 

the  Snellen  test  to  have  Y.  otf^  in  both  eyes.  I 
found  that  with  either  i3liis  or  minus  spherical,  the 
vision  is  very  little  improved,  neither  could  I  get 
any  better  result  by, using  cylinders  over  them,  so 
I  suspected  mixed  astigmatism,  more,  I  may  add, 
as  a  result  of  an  ophthalmoscopic  examination 
than  from  any  other  reason,  so  I  tried  cross  cylin- 
ders on  her,  using  a  -^.75  in  the  vertical  meridian, 
and  a  — 2  in  the  horizontal  meridian,  so  after  sev- 
eral trials  and  changes,  I  find  this  to  be  the  best, 
giving  her  |^  vision  in  both  eyes,  and  the  chart 
showed  the  lines  distinct  in  all  meridians. 

The  retinoscope  proved  the  result,  so  instead 
of  ordering  the  cross  cylinders,  I  prescribed  the 
following  combination,  which  with  a  little  study 
you  will  understand:— 2  D.  S.'C  -r-2.75  D.  Cyl.  Ax. 
90°  both  eyes. 

You  M'ill  ask  why  I  did  this,  so  I  must  ex- 
plain. Well,  as  she  is  2D.  myopic  in  only  one  meri- 
dian, and  0.75D.  hypermetropic  in  the  other,  the 
2D.  spherical  will  not  only  correct  this  myopic 
meridian,  but  it  will  remove  the  hj'permetropic 
meridian  just  so  much  further  from  emmetropia, 
or  in  other  words,  makes  the  other  meridian  2D. 
more  hypermetropic,  which  in  all  will  amount  to 
2.75D.  hypermetropia.  This  you  will  find,  if  you 
take  the  trouble  to  reduce  or  measure  it,  is  of  the 


ASTIGMA  TISM.  75 

saDie  power  as  the  cross  cylinders  would  be,  and 
at  the  same  time  much  cheaper  and  just  as  good. 

On  looking  up  the  statistics  on  mixed  astig- 
matism, I  find  some  writers  claim  a  greater  fre- 
quency for  it,  eyen  placing  it  ahead  of  simple  my- 
opic astigmatism.  Howeyer  this  may  be,  it  does 
not  accord  with  my  experience,  and  that  is  all  I  am 
aiming  at  in  this  little  book. 

In  concluding  this  subject  of  refraction 
in  general,  a  few  obseryations  may  not  be  amiss. 
In  the  aboye  case  just  cited  of  mixed  astigmatism, 
you  may  ask  why  we  did  not  secure  better  yision 
than  If.  That  I  cannot  tell,  but  it  was  probably 
owing  to  a  defectiye  perception  on  the  part  of  the 
eye,  or  it  may  be  owing  to  some  condition  that  will 
improye  by  the  use  of  glasses,  and  that  later  on  we 
may  be  able  to  do  better  for  her.  There  are  many 
cases,  howeyer,  of  refractiye  errors  in  which  you 
will  not  be  able  to  procure  yision  of  tf?  ^^^  in 
these  cases  you  must  be  satisfied  with  the  best  re- 
sults you  can  obtain.  Now%  in  cases  of  anisome- 
tropia, where  there  is  a  great  difference  in  the  cor- 
recting glass  for  each  eye,  I  do  not,  as  a  rule,  cor- 
rect fully  the  poor  eye,for  I  find  that  only  a  few  per- 
sons can  tolerate  glasses  in  which  there  is  a  differ- 
ence of  seyeral  dioptres.  In  these  cases  it  is  best 
to  keep  the  glasses  within  one  or  one  and   a  half 


76      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

dioptres  of  each  other,  and  perhaps  later  on  when 
the  patient  shall  have  become  familiar  with  them, 
Tou  can  increase  the  strength  of  the  lens  over  the 
weaker  eve,  in  the  hope  of  being  able  to  develop  a 
greater  acuteness  of  vision  in  that  eye. 

With  this,  then,  we  will  conclude  this  chap- 
ter, and  proceed  to  take  np  a  consideration  of  the 
other  tests  used  in  the  determination  of  the  differ- 
ent refractive  conditions,  and  the  first  to  engage 
our  attention  will  be  the  ophthalmoscope.  We 
have  adopted  this  method  of  considering  the  dif- 
ferent tests  under  a  separate  heading,  rather  than 
to  jumble  them  by  bringing  them  altogether  under 
one,  thus  confuse  the  student  and  make  the  subject 
ai^pear  more  difficult  of  comprehension  than  it 
really  is.  We  hope  this  arrangement  will  com- 
mend itself  to  the  reader. 


DE  ZENG^S  REFRACTOMETER. 


Figure  12. 


The  above  represents  a  new  instrument  recently  introduced  to 
the  profession  by  the  Cataract  Optical  Company,  of  Buffalo,  N.  Y., 
called  the  Refractometer.  By  the  aid  of  this  instrument  they  claim 
that  all  refractive  errors  of  the  eye,  and  especially  latent  hyper- 
metropia,  can  be  readily  detected  without  the  use  of  a  mydriatic. 

This  claim  seems  to  be  pretty  well  confirmed  by  those  who  have 
used  the  instrument. 

In  presenting  it  to  the  consideration  of  the  profession,  the  manu- 
facturers have  this  to  say  :  "In  offering  the  Refractometer  to  the 
profession,  we  do  so  feeling  that  it  meets  the  long-felt  want  of  an 
instrument  capable  of  diagnosing  and  measuring  the  refractive 
errors  of  the  eye,  quickly,  accurately,  and  in  the  majority  of  in- 
stances exactly,  without  the  assistance  of  a  mydriatic.  The  optical 
and  mechanical  construction  of  the  instrument  are  such  as  to  insure 
precision  in  all  its  measurements  and  a  permanency  in  the  adjust- 
ment of  its  parts,  all  of  which  are  formulated  on  the  most  scientific 
principals  involved  in  modern  microscopical  construction.  Believing 
that  in  practice  it  will  demonstrate  its  superiority  over  other  refract- 
ing instruments,  we  are,  «S5C." 

rr 


CHAPTER  VII. 


Opbthalnioscopj'. 

Q.     What  is  oplithalmoscopy? 

A.  It  is  a  method  of  examining  the  interior 
of  the  eve  by  means  of  an  instrument  called  the 
ophthalmoscope,  in  order  to  determine  its  condi- 
tion as  to  health  and  refraction. 

Q.  When  and  by  whom  was  the  ophthalmo- 
scope introduced  for  this  purpose? 

A.     By  Prof.  Melmholtz,  in  the  year  1S51. 

O.  What  was  its  construction  as  originally 
invented  and  introduced  by  Professor  Helmholtz? 

A.  Simply  that  of  a  plain  mirror,  with  a  hole 
in  the  center. 

Q.  Has  there  been  an  improvement  in  the 
make  of  the  ophthalmoscope  since  its  first  intro- 
duction? 

A.  Yes;  there  have  been  many  changes  and 
improvements  made  in  the  instrument  since  then, 
and  many  varieties  of  it  can  be  found  on  the  mar- 
ket at  the  present  time. 


OPHTHALMOSCOPY. 


79 


Q.     What  particular  instrument  is  most  gen- 
erally used  at  the  j)reseut  day? 

A.     The    Loring    ophthalmoscope,    or    some 
modification  of  it. 

Q.     What  is  the  mechanical   construction  of 
the  Loring  ophthalmoscope? 
Figure  13. 


Loring's  Complete  Ophthalmoscope,   with    quadrant  and 
tilting  mirror. 


80      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

A.  It  consists  of  a  rectangular  mirror  slight- 
ly concave,  with  a  hole  in  the  center.  This  mirror 
is  so  attached  as  to  be  able  to  be  tilted  to  the  right 
or  left,  as  the  case  may  require.  Behind  this  mir- 
ror is  a  rotating  disk  containing  a  series  of  convex 
and  concave  lenses,  from  1  to  ID.  in  convex,  and 
from  1  to  8D.  concave.  The  disk  can  be  rotated  so 
as  to  bring  any  one  of  these  lenses  before  the 
aperture  in  the  mirror  when  needed.  Still  behind 
this  circular  disk  is  a  quadrant  carrying  four 
lenses,  a — .Sand  a  — 16  D.  and  a -I -.5  and  a-^lQ  D. 
This  quadrant  can  be  rotated  also,  so  as  to 
bring  any  of  these  lenses  before  the  aperture, 
either  alone  or  in  combination  with  the  lens  in  the 
disk,  so  we  can  get  an}'  combination  we  desire 
from  0.5  to  23D.  convex  and  .5  to  24D.  concave. 
The  instrument  is  arranged  with  a  removable  han- 
dle, thus  enabling  it  to  be  carried  in  a  small  case. 

Q.  How  many  methods  are  there  in  using 
the  ophthalmoscope? 

A.  There  are  two  methods,  the  direct  and 
indirect.  In  the  direct  method  you  obtain  an 
erect,  or  upright  image  of  the  retina,  while  with 
the  indirect  method  you  get  an  inverted  image  of 
the  retina. 

Q.  How  do  you  proceed  to  examine  the  eye 
with  the  direct  method? 


OPHTHALMOSCOPY.  81 

A.  You  first  darken  your  room,  if  you  have 
not  a  special  clarlv  room  for  this  purpose,  and  seat 
your  patient  with  his  back  to  the  source  of  light. 
An  ordinary  Argand  burner,  or  any  other  good 
light  is  suitable  for  this  work.  The  light  must  be 
at  the  side  of  the  head  and  back  far  enough  so  as 
to  leave  the  face  in  shadow.  The  light  and  exam- 
iner must  be  on  the  same  side  as  the  eye  under  ex- 
amination, and  the  examiner  must  use  his  right 
eye  in  examining  the  i^atient's  right,  and  left  when 
examining  the  left,  unless  there  is  some  good  rea- 
son for  not  doing  so.  Now  there  are  several  things 
you  must  observe  before  i^roceeding  to  examine 
the  fundus — that  is,  you  must  note  the  condition  of 
the  cornea,  the  lens,  and  the  vitrious;  you  must  de- 
termine as  to  whether  they  are  perfectly  transpar- 
ent, clear  and  free  from  spots  and  specks.  You  can 
best  observe  this  by  directing  the  light  on  the  cor- 
nea at  a  distance  of  say  two  feet  or  twenty  inches, 
and  this  is  facilitated  by  the  aid  of  a  plus  lens,  of 
say,  6  or  7  D.  behind  the  aperture  of  the  ophthal- 
moscope. 

By  moving  the  mirror  of  the  ophthalmoscope 
a  little  from  side  to  side  so  as  to  make  the  light 
play  over  the  cornea  and  pupil,  you  will  readily 
see  any  spots  that  may  be  on  the  cornea  or  lens. 
This  may  be  made  still  more  distinct  by  the  meth- 
od called  oblique  illumination,  w^hich  consists  of 


82      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

condensing  a  light  on  the  cornea  by  means  of  a 
convex  lens  of  ISD.  Spots  that  are  not  clearly 
seen  by  means  of  the  ophthalmoscopic  mirror  can 
be  readily  made  out  by  this  means.  If  the  cornea 
and  lens  are  clear,  you  examine  the  yitrious  for 
floating  bodies  by  looking  from  this  same  distance, 
and  haye  the  patient  roll  the  eyes  in  different  di- 
rections— up,  down,  and  sidewise,  holding  them  in 
each  position  for  a  few  seconds  will  cause  a  gravi- 
tation of  specks  or  floating  bodies  (muscae  yoli- 
tantes),  and  as  they  pass  they  can  be  plainly  seen. 
You  can  generally  find  these  ''floating  bodies''  in 
high  degrees  of  myopia,  and  they  should  always  be 
looked  for,  as  they  afford  us  some  idea  of  how  much 
change  of  a  pathological  character  has  taken  place 
in  a  given  case,  and  as  you  will  find  many  patients 
complaining  of  seeing  them,  it  is  best  for  you  to 
learn  how  to  detect  them  with  the  ophthalmo- 
scope. 

After  having  examined  the  media  thor- 
oughly, you  rotate  your  disk  so  as  to  bring  the 
aperture  before  your  eye,  and  directing  a  steady 
light  on  the  pupil  of  the  patient's  eye,  you  slowly 
approach  your  patient  until  you  are  within  an  inch 
or  so  of  his  eye,  and  you  will  then  notice  the  red 
fundus  with  the  blood  vessels  running  in  different 
directions,  and  the  soft  velvety  appearance  of  the 
retina  called  the  tapetum.    You  can  now  readily 


OPHTHALMOSCOPY 


83 


^ee  the  entrance  of  the  optic  nerve  and  the  disk 
with  the  vessels  passing  over  it  in  various  direc- 
tions, and  toward  the  temporal  side  of  the  disk, 
and  on  a  line  with  its  lower  border,  at  a  distance 
equal  to  about  twice  the  diameter  of  the  nerve 

Figure  14. 


Showing  the  direct  method  of  making  an  ophthalmoscopic  exam, 
ination.     (After  Noyes.) 

head,  or  disk,  you  will  notice  the  macula  lutae,  or 
"yellow  spot,"  characterized  by  its  freedom  from 
blood  vessels  and  its  darker  color.  This  is  the 
spot  where,  ordinarily,  the  focus  of  the  images  are 
formed,  and  which  is  most  concerned  in  the  physi- 
ological phenomenon  of  sight. 

You  will  also  notice  the  appearance  of  the  re- 
tina and  its  uniformity  of  color,  its  freedom  from 
abnormal  pigmentation  and  silvery  spots,  the  latter  of 
which  has  marked  significance  as  resjards  disease 


84      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

of  the  kidneys,  either  Bright's  or  Diabetis.  Ob- 
serve the  nerve  head  and  note  if  it  has  a  cupped 
appearance  or  if  the  blood  vessels  cross  its  bor- 
der boldly  and  from  the  center,  or  seem  to  climb  up 
around  the  edge  of  the  disk;  notice  the  shape  of 

FiGDRE   15. 


Showing  the  indirect  method  of  making  an  ophthalmoscopic  exam- 
ination. (After  Koyes.) 


the  disk  also,  if  it  be  round  or  oval  in  shape,  the  lat- 
ter indicating  astigmatism.  Look  for  posterior 
staphyloma,  or  a  crescent-shaped  drawing  away  of 
the  retina  from  the  choroid,  frequently  found  in 
myopia.  Every  one  should  learn  to  observe  these 
things  when  examining  the  fundus.  This  is,  of 
course,  onh-  for  the  purpose  of  determining  the 
condition  of  the  different  parts  of  the  eye  as  to 
health.    The  determination   of  its  refraction  we 


-OPHTHALMOSCOPY.  85 

will  describe  shortly.    This  is  the  direct  method 
^nd  all  images  are  erect. 

FiGUUE   16. 


^lood  vessels  of  the  retiua,  showing  also  the  optic  disk  to  side,  with 
the  macula  lutea  in  the  center.     (After  Testut.) 

Now,  in  the  indirect  method,  we  get  back  from 
the  patient,  sav  18  inches,  and  a  convex  lens  of 
2^  inches  focal  distance,  is  held  at  about  its  focal 
distance  from  the  patient's  eye.  Some  practice 
will  be  necessary  for  you  to  get  a  distinct  image  of 
the  retina.  You  can  bring  out  the  image  more  dis- 
tinctly by  using  a  convex  lens  of  the  ophthalmo- 
scope before  the  aperture,  say  of  4  or  5D.  When 
you  do  get  a  distinct  picture,  you  must  not  forget 
that  everything  is  upside  down,  or  that  you  see  an 
inverted  image  of  the  retina.  I  am  sure  you  will 
And  this  indirect  method  more  difficult  to  accom- 


86      REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

plish;  still  bv  considerable  practice  you  can  mas- 
ter it  all  rigbt.  You  will  find  it  mucb  easier  to  ex- 
amine bigbly  myopic  eyes  witli  tbis  metbod  tban 
witb  tbe  direct  metbod,  but  for  determining  tbe  re- 
fractive conditions  of  tbe  eye  and  proving  your 
otber  tests  by  means  of  opbtbolmoscopy,  I  would 
advise  you  to  confine  yourself  to  tbe  direct  metb- 
od— wbicb  we  sball  now  proceed  to  describe  in 
detail,  taking  up  an  illustrative  case  of  eacb  va- 
riety of  refraction  to  belp  us  to  more  fully  under- 
stand it. 

Q.  How  do  we  determine  tbe  presence  of 
emmetropia  by  examining  tbe  eye  witb  tbe  opb- 
tbalmoscope? 

A.  In  order  to  correctly  measure  tbe  refrac- 
tive condition  of  a  patient's  eye  by  means  of  tbe 
opbtbalmoscope,  two  conditions  are  absolutely 
essential  on  tbe  part  of  tbe  examiner.  First,  be 
must  bave  an  emmetropic  eye  bimself ;  tbat  is,  if  be 
is  not  emmetropic  by  nature,  be  must  make  bim- 
self so  by  proper  correcting  lens;  or  if  not,  be  must 
take  tbis  into  consideration  wben  measuring  tbe 
patient's  refraction,  but  if  be  be  astigmatic,  tbe 
only  way  is  to  wear  correcting  cylindric  lens  dur- 
ing tbe  examination;  but  if  tbe  examiner  be  sim- 
ply myopic  or  bypermetropic,  be  can  take  tbis  into 
account  if  be  does  not  wear  correcting  lens  bim- 
self, remembering  tbat  wbatever  amount  of  byper- 


OPHTHALMOSCOPY.  87 

tropia  the  examiner  may  have  will  neutralize  just 
so  much  myopia,  or  if  he  is  myopic,  it  will  neutral- 
ize the  same  amount  of  hypermetropia  in  the  pa- 
tient's eye;  for  example,  if  the  examiner  be  2D.  hy- 
permetropic, it  will  neutralize,  or  overcome,  2D. 
of  myopia  in  the  patient's  eye,  and  if  the  examiner 
be  2D.  myopic,  it  will  overcome  2D.  of  hyperme- 
tropia in  the  patient. 

The  second  condition  necessary  to  the  accur- 
ate measurement  of  refraction  with  the  ophthal- 
moscope is  a  complete  relaxation  of  the  accommo- 
dation of  the  examiner's  eye.  This  you  can  only 
accomiDlish  by  experience  and  practice.  A  sense 
of  complete  relaxation  of  the  accommodation  may 
be  experienced  by  looking  off  into  infinity  without 
fixing  your  eye  upon  any  object  particularly.  Ev- 
erything under  this  condition  appears  hazy.  Now, 
if  you  hold  your  finger  before  your  eye,  say  at  10 
inches,  instead  of  seeing  one,  you  will  see  two  fin- 
gers, showing  that  not  only  the  accommodation  is 
relaxed,  but  that  there  is  no  effort  at  convergence, 
thus  allowing  each  eye  to  see  an  image  of  its  own. 
By  a  little  practice  you  will  learn  to  appreciate 
this  sensation  of  relaxation,  and  this  must  be  the 
condition  of  your  own  eye. when  using  the  ophthal- 
moscope. 

In  using  the  ophthalmoscope  to  measure  the 
refraction  of  an  eye,  it  is  necessary  for  us  to  have  a 


88      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

land-mark,  as  ir  M'ere,  to  enable  ns  to  accurately 
determine  the  refraction  in  the  two  principal  meri- 
dians, that  is,  in  the  meridians  of  greatest  and 
least  curvature,  usually  to  be  found  in  the 
vertical  and  horizontal.  For  this  purpose  the 
minute  blood  vessels  that  cross  at  right 
angles  in  the  horizontal  and  vertical  meri- 
dians, are  taken  as  a  land-mark.  We  must  be  able 
to  see  the  small  vessels  clearly  without  any  effort 
on  the  part  of  our  own  accommodation  before  we 
can  arrive  at  any  conclusion  as  to  the  refraction  of 
the  eye  under  examination.  When  the  greatest 
and  least  curvature  are  at  any  other  meridian  than 
the  horizontal  and  vertical,  then  the  lines  in  these 
meridians  must  be  selected  for  land-marks. 

In  a  previous  chapter  you  have  seen  that  light 
reflected  from  the  retina  of  an  emmetropic  eye, 
emerges  in  parallel  lines,  so  with  your  ophthalmo- 
scope before  an  emmetropic  eye,  you  are  able  to  see 
the  details  of  the  fundus  withotit  any  trouble,  but 
if  you  should  place  a  convex  lens  before  the  oph- 
thalmoscope, you  would  produce  a  convergence  of 
the  emergent  rays,  and  your  emmetropic  eye  could 
not  focus  them  on  your  retina;  hence  the  rule  is 
that  when  you  see  the  fundus  clearly  through  the 
aperture  of  the  ophthalmoscope,  btit  which  blurs 
or  becomes  indistinct  when  a  convex  lens  of  ID.  is 
placed  before  the  aperture  of  the  ophthalmoscope, 


OPHTHALMOSCOPY.  89 

that  the  eye  under  examination  is  emmetropic,  and 
you  will  not  need  a  correcting  glass.  Still  as  you 
use  the  ophthalmoscope  more  to  prove  the  accur- 
acy of  the  test  by  the  trial  lens,  you  have  perhaps 
already  found  that  out. 

Q.  How  is  one  to  recognize  the  difference  be- 
tween emmetropia  and  hypermetropia  with  the 
ophthalmoscope  ? 

A.  We  have  previously  learned  that  the  hy- 
permetropic eye  emits  divergent  rays.  In  that 
case  you  can  readily  understand  that  with  your 
emmetropic  eye  and  your  accommodation  that  you 
will  still  be  able  to  see  the  fundus  clearly,  as  in 
emmetropia,  through  the  aperture  of  the  ophthal- 
moscope. But  we  have  just  seen  that  in  emme- 
tropia the  placing  of  a  convex  lens  behind  the 
aperture  of  the  ophthalmoscope  would  blur  the 
fundus.  Now,  in  hypermetropia  this  does  not  oc- 
cur, but  you  can  still  see  the  small  vessels  of  the 
fundus  after  placing  a  plus  lens  before  the  aper- 
ture, but  you  keep  on  increasing  the  strength  of 
the  lens  behind  the  aperture,  and  pretty  soon  you 
will  reach  one  strong  enough  to  blur.  Well,  this  is 
the  measure  of  the  amount  of  hypermetropia, 
so  we  can  formulate  a  rule  for  the  determination 
and  for  the  approximate  estimation  of  the 
amount  of  hypermetropia  as  follows:  In  looking 
through  the  aperture  of  the  ophthalmoscope  into 


90      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

a  hypermetropic  eye,  you  can  see  the  details  of  the 
fundus  clearly,  and  that  the  Strongest  convex  lens 
placed  behind  the  aperture  of  the  ophthalmoscope, 
that  will  allow  a  distinct  view  of  the  small  vessels 
of  the  fundus,  will  represent  the  amount  of  hyper- 
metropia.  For  example,  a  young  lady,26  years  old, 
complaining  of  her  eyes,  sought  aid  for  her  vision. 
With  the  Snellen  test  she  accepts  a  —1.50  D.  S., 
shoAving  this  to  be  the  amount  of  her  manifest  hy- 
permetropia.  Ophthalmoscopic  examination 
through  the  aperture  reveals  a  distinct  fundus,and 
by  rotating  a  convex  lens  behind  the  aperture,  we 
find  they  remain  distinct  with  a  convex  lens  of  4D. 
behind  the  aperture,but  any  stronger  lens  causes  a 
blurring,  hence  this  4D  represents  her  total  hyper- 
metropia.  So  you  see  this  is  a  ready  way  of  differ- 
entiating between  emmetropia  and  hypermetrop- 
ia;  in  the  former  condition,  convex  lenses  cause  a 
blurring,  while  in  the  latter  case  they  do  not,  until 
-the  lens  is  reached  strong  enough  to  measure  the 
total  hypermetropia. 

Q.  What  rule  have  we  then  by  which  we  can 
distinguish  between  simple  hypermetropic  astig- 
matism and  simple  hypermetropia? 

A.  A  very  simple  rule,  indeed,  if  you  will 
only  remember  that  in  simple  hypermetropic  as- 
tigmatism one  of  the  meridians  of  the  eye  is  emme- 


OPHTHALMOSCOP  Y.  91 

tropic  and  the  other  is  hypermetropic.  This 
emmetropic  mericliafl  sends  out  parallel  rays, 
while  the  hypermetropic  meridian  emits  divergent 
rays.  In  the  emmetropic  meridian  joii  can 
see  the  fundus  clearly  through  the  aperture,  but  a 
plus  lens  will  blur  this  meridian  when  placed  be- 
hind the  aj^erture.  In  the  hypermetropic  meri- 
dian you  can  also  see  the  fundus  clearh^,  but 
a  plus  lens  placed  behind  the  aperture  of  the  oph- 
thalmoscope will  not  blur,  and  the  strongest  con- 
vex lens  through  which  you  can  still  see  the  small 
vessels  in  the  hypermetropic  meridian  will  repre- 
sent the  amount  of  astigmatism. 

For  example,  you  have  a  case  in  which  the  hor- 
izontal meridian  is  clearly  seen  through  the  aper- 
ture, but  a  convex  lens  of  ID.  will  cause  a  blur- 
ring. Now  in  the  vertical  meridian  you  can  also 
see  distinctly  through  the  aperture,  and  by  plac- 
ing a  convex  lens  of  2D.  behind  the  aperture,  yoiL 
are  still  able  to  see  distinctly  in  the  vertical,  but'*- 
e^ery thing  is  blurred  and  indistinct  in  the  hori- 
zontal meridian.  This  lens  then,  that  is  2D.,  will 
represent  the  amount  of  astigmatism,  and  the  axis 
of  the  corresponding  cylinder  lens  must  be  placed 
parallel  to  the  meridian  seen  distinctly  with  the 
strongest  lens,  and,  as  in  this  case,  we  find  this  to 
be  in  the  vertical  meridian  the  axis  of  the  correct- 
ing cylinder  lens  must  be  placed  in  the  vertical 


92      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

meridian,  thus  i)roYing  that  our  case  is  one  of  sim- 
ple hypermetropic  astigmatism,  "according  to  the 
rule,"  or  at  90°. 

If  this  should  happen  to  be  a  case  of  com- 
pound hypermetropic  astigmatism,  all  that  is 
necessary  for  you  to  remember  is  that  the  emer- 
gent rays  of  this  eye  are  divergent  in  both  meridi- 
ans, but  more  divergent  in  one  meridian  than  in 
the  other.  It  will  then  require  a  convex  glass  of 
different  strength  to  measure  the  two  separate 
meridians,  and  the  first  glass  will  represent  the 
amount  of  the  hypermetropia,  while  the  second 
will  not  only  measure  the  hypermetropia,  but  will 
measure  it  plus  the  astigmatism,  and  the  differ- 
ence in  the  two  convex  lenses  will  represent  the 
amount  of  astigmatism.  For  example,  if  you  can 
see  the  horizontal  meridian  distinctly  with  a  plus 
2D.  and  the  vertical  meridian  is  still  distinct  with 
a  plus  4D.,  but  the  horizontal  is  blurred  and  indis- 
tinct, then  the  difference  between  the  two  lens, 
that  is  2D.,  will  represent  the  amount  of  astigma- 
tism, and  as  the  axis  of  the  correcting  cylinder  lens 
must  be  placed  parallel  to  the  meridian  seen  with 
the  strongest  glass,  we  have  for  a  correcting  glass 
the  following  formula: 

-I-  2  D.  S.  C  w-  -I-  2  D.  cyl.  Ax.  90°, 
thus  clearly  proving  to  us  a  case  of  compound  hy- 
permetroj^ic  astigmatism. 


OPHTHALMOSCOPY.  93 

Q.  How  do  you  determine  myopic  conditions 
by  the  use  of  the  ophthalmoscope? 

A.  In  speaking  of  myopia  in  a  former  chap- 
ter, we  have  seen  that  as  the  principal  focus  of  the 
myopic  eye  was  in  front  of  the  retina,  reflected 
rays  from  the  retina,  coming  from  a  ijoint  further 
than  its  principal  focus  causes  a  convergence  of 
the  emergent  rays,  and  as  converging  rays 
cannot  enter  your  emmetropic  eye,  they 
must  be  first  rendered  parallel,  and  this  is 
done  by  the  use  of  the  concave  lens  of  the  ophthal- 
moscope. The  rule,  then,  to  determine  simple  my- 
opia is  that  the  w^eakest  concave  lens  that  will  ren- 
der the  fundus  clear  and  distinct  will  measure  the 
amount  of  myopia. 

For  example,  supposing  you  have  a  case  in 
which  everything  about  the  fundus  of  the  eye  is 
blurred  when  looking  through  the  aperture,  and 
you  find  that  the  use  of  convex  lens  makes  it 
worse.  Now  you  try  a  concave  lens  and  you  find 
that  things  begin  to  look  clearer;  you  finally  con- 
tinue increasing  the  strength  of  the  lens  behind 
the  aperture  until  the  very  weakest  lens  is 
reached,  that  enables  you  to  see  the  details  of  the 
fundus  distinctly,  and  you  find  this  to  be  a  concave 
lens  of  4D. ;  then  you  have  a  case  of  simple  myopia 
of  4E). 


94      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

If  you  have  a  case  of  simple  myopic  astig- 
matism in  one  meridian  the  eye  is  emmetropic, 
while  in  in  the  other  it  is  myopic.  In  the  emme- 
tropic meridian  you  can  see  the  fundus  distinctly 
through  the  aperture,  while  it  requires  a  concave 
lens  of  ID.  to  see  in  the  myopic  meridian  distinct- 
ly, this  then  will  represent  the  amount  of  astig- 
matism, and  the  axis  of  the  correcting  cylinder 
lens  must  be  placed  parallel  to  the  myopic  meridi- 
an; for  example,  supposing  you  can  see  the  vertical 
meridian  clearly  through  the  aperture,  while  it  re- 
quires a  concave  lens  of  ID.  to  see  the  horizontal 
meridian  distinctly,  this  then  being  the  very  weak- 
est glass  that  renders  them  distinct  will  represent 
the  amount  of  astigmatism,  and  the  axis  of  the 
correcting  cylinder  lens  must  be  placed  parallel  to 
this  meridian,  or  at  180°,  thus  showing  us  a  case  of 
simple  myopic  astigmatism  "according  to  the 
rule,"  or  at  l<SOo. 

In  compound  myopic  astigmatism,  the 
emergent  rays  in  both  principal  meridians  are  con- 
verging, but  more  converging  in  one  than  in  the 
other,  so  if  it  requires  a  minus  spherical  of  2D.  to 
see  the  vessels  in  the  vertical  meridians  and  one  of 
5D.  to  see  them  distinctly  in  the  horizontal,  the 
five  dioptres  measure  the  amount  of  general  my- 
opia plus  the  astigmatism,  and  the  difference  in 
the  two  lenses,  namely,  3D.,will  give  us  the  amount 


OPHTHALMOSCOPY.  95 

of  astigmatism;  and  as  in  simple  myopic  astigma- 
tism, the  axis  of  the  correcting  cylinder  lens  must 
be  parallel  to  the  meridian  of  greatest  ametropia, 
or  in  this  case  in  the  horizontal,  or  at  180°,  we 
have  for  a  correcting  glass  for  this  case  of  com- 
pound myopic  astigmatism,  the  following  formula: 

—2  D.  S.  C  —3  D.  Cyl.  Ax.  180°. 

Remember  ahvays  to  use  the  weakest  concave 
lens  that  renders  the  fundus  distinct  in  myopic 
conditions. 

Yoii  will  find  the  diagnosis  of  mixed  astigma- 
tism with  the  ojjhthalmoscope  perhaps  as  easy,  if 
not  more  so,  than  any  other  compound  conditions, 
as  you  have  simply  to  deal  with  hypermetropia  in 
one  of  the  principal  meridians,  and  with  myopia 
in  the  meridian  at  right  angles  to  this  one,  and  you 
proceed  to  measure  it  by  using  the  strongest  con- 
vex in  the  hypermetropic  meridian,  and  the  weak- 
est concave  glass  in  the  myopic,  and  the  correcting 
glass  will  be  determined  by  the  result  you  obtain 
corroborated  by  the  several  tests  that  we  have  ex- 
plained or  enumerated. 

With  this,  then,  we  will  conclude  this  chapter 
on  ophthalmoscopy.  Trusting  that  by  the  use  of 
simple  language  we  may  facilitate  the  study  of 
this  method  of  diagnosing  the  pathological  and  re- 
fractive conditions  of  the  human  eye. 


CHAPTER  VIII. 


Oplithalinoiuetry. 

Q.     What  is  ophthalmometry? 

A.  It  is  a  method  of  measuring  the  different 
diameters  of  the  human  eye  during  life. 

Q.  What  is  its  special  application  in  relation 
to  refraction? 

A.  Its  special  application  is  the  determina- 
tion of  corneal  astigmatism,  by  means  of  measur- 
ing the  radii  of  the  principal  meridians  of  the 

cornea. 

■ji- 

Q.  To  whom  is  tL  credit  due  for  first  utiliz- 
ing this  method  in  refractive  work? 

A.  To  Professor  Helmholtz,  in  the  year  1854, 
three  years  after  his  introduction  of  the  ophthal- 
moscope. 

Q.  What  ophthalmometer  is  mostly  in  use  at 
the  present  time? 

A.     The  Java!  and  Schiotz  instrument. 

Q.  What  is  the  mechanical  construction  of 
the  Javal  ophthalmometer? 

96 


OPHTHALMOMETR  Y 
Figure  17. 


97 


JaVAL  &   SCHIOTZ'   OpHTxIALMOMETER  . 

This  instrument  has  the  perpend'^ular  adjustment,  by  means  of 
a  rack  and  pinion  movement  attache  to  the  upright  cohimn.  The 
mo vablo  mire  has  rack  and  pinion  adjustment  and  the  lens  is  pro- 
tested by  an  extra  long  tube,  which  is  provided  with  a  brass  cap  to 
cover  it  when  not  in  use.  This  instrument  has  a  finely  enamelled 
dial,  which  does  not  change  color  with  use  but  retains  its  whiteness. 
It  is  also  provided  with  a  small  indicating  dial  at  the  back,  so  that 
the  position  of  the  mires  can  easily  be  observed  by  the  operator. 
The  improved  metal  head-piece  is  provided  with  Skeels  swinging 
eye  shield,  and  an  adjustable  chin  rest  which  carries  a  glass  arti- 
ficiftl  cornea.  The  instrument  has  the  proper  fittings  for  electric 
light  illumination,  except  the  lamps,  which  are  furnished  by  the 
company  from  whom  the  current  is  obtained. 

A.     Its  principal  jDarts  consist  of  a  reversing 
telescope,  in  the  center  of  which,  and  about  mid- 


98      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

way  between  the  two  convex  lens,  is  a  double  re- 
fracting prism,  called  the  Wollaston  prism,  which 
"consists  of  two  quartz  prisms,  so  cut  that  when  in 
position,  the  apex  of  each  is  at  the  base  of  the  oth- 
er and  the  optical  angle  of  each  is  at  right  angles 
to  that  of  the  other  and  to  the  axis  of  vision."  A 
large  enamelled  disk  with  the  degrees  numbered 
from  0  to  180°,  in  inverted  characters,  on  its  per- 
iphery, while  the  rest  of  the  disk  from  the  numbers 
to  the  center,  is  a  series  of  concentric  circles  in 
white, while  the  background  is  black  enamel.  These 
circles  correspond  to  a  difference  of  5°  from  5°  to 
45°.  The  disk  is  penetrated  by  the  telescope  at  its 
center.  Attached  to  the  telescope  is  an  arc  which 
rotates  when  the  telescope  is  turned  around  the 
surface  of  the  large  disk.  On  this  arc  are  two 
sights,  or  mires,  one  rectangular  in  shape,  the  oth- 
er cut  into  a  series  of  steps,  each  step  measuring  six 
millimetres  in  width.  Formerly  one  of  these 
mires  was  fastened  to  the  arc,  while  the  other 
was  readily  movable  along  the  arc,  but  by  an  ar- 
rangement suggested  by  Professor  Francis  Yalk 
of  New  York  city,  both  mires  are  made  to  move 
toward  or  from  each  other  by  a  milled  screw.  This 
he  calls  the  double  movable  mires.  Attached  to 
each  mire  is  a  short  white  pointer,  while  at  the  cen- 
ter of  the  arc,  and  at  right  angles  to  the  short 
pointers,  is  a  long,  white  pointer.    The  mires  are 


OPHTHALMOMETRY.  99 

white  enamelled,  mounted  on  a  background  of 
black  velvet.  These  three  principal  parts,  that  is, 
the  telescope,  the  disk,  and  the  arc,  rest  by  means 
of  a  tripod  on  a  i)latform. 

By  means  of  an  adjustable  screw,  the  tele- 
scope can  be  adjusted  in  the  vertical  position, 
while  the  horizontal  adjuvstment  is  secured  by  mov- 
ing it,  as  a  whole,  from  side  to  side  on  the  plat- 
form. The  rest  of  the  instrument  consists  of  an 
upright  chin  rest,  with  a  drop  shade  for  the  pur- 
pose of  covering  the  eye  that  is'  not  being  exam- 
ined. When  in  use,  the  instrument  is  placed  on  a 
stand  or  table  of  suitable  height,  so  that  it  can  be 
used  without  straining  or  effort  on  the  part  of  the 
examiner. 

It  may  be  here  remarked  that  the  letters  and 
figures  painted  upon  the  disk  upside  down,  appear 
right  side  up  after  being  reflected  from  the  cornea 
and  observed  through  the  reversing  telescope. 

Q.  How  do  you  use  the  ophthalmometer,  and 
by  what  method  do  you  determine  the  presence  or 
absence  of  astigmatism? 

A.  You  begin  by  seating  your  patient  so  as 
to  have  his  chin  rest  comfortably  on  the  chin  rest 
of  the  instrument,  and  the  head  in  such  a  position 
as  to  bring  the  two  eyes  on  a  level,  and  the  eye  to 
be  examined  before  the  telescope,  while  the  other 


100    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

eye  is  covered  with  the  shade  provided  for  that 
purpose.  You  then  rotate  the  ocular  of  the  tele- 
scope until  you  obtain  a  clear  and  distinct  view  of 
the  two  spider  lines  which  cross  at  right  angles, 
and  which  are  for  the  purpose  of  focusing  the  ocu- 
lar. When  the  ocular  is  focused  and  the  telescope 
properly  adjusted,  you  can,  by  looking  through  the 
telescope,  get  a  clear  and  distinct  picture  of  the 
disk  and  mires  as  reflected  from  the  cornea.  You 
will  now  observe  the  figures  to  be  right  side  up,  by 
the  reversing  action  of  the  telescope.  You  will  al- 
so observe  that  instead  of  one  picture  of  the  disk 
and  mires,  you  will  see  two,  one  overlaj)ping  the 
other,  and  you  will  also  notice  two  more  indistinct 
images  at  the  periphery  of  the  disk. 

To  these  periiiheral  images  no  attention  is  to 
be  paid,  but  the  two  central  ones  must  engage  our 
full  attention,  and  we  must  be  able  to  see  them 
clearly  and  distinctly  without  any  effort  on  our 
part,  or  any  straining  of  our  accommodation. 

Each  mire  is  provided  with  what  is  called  a 
guide-line,  which  passes  straight  through  its  cen- 
ter. We  turn  the  arc  until  these  two  lines  of  the 
mire  will  come  together,  as  it  were,  to  form  one 
continuous  line.  When  these  two  lines  become 
continuous,  we  bring  the  edges  of  the  mires  to- 
gether, as  it  were,  to  form  one  continuous  line. 
When  these   two    lines   become    continuous,  we 


OPHTHALMOMETRY.  101 

bring  tlie  edges  of  the  mires  together  by  means  of 
the  thumb-screw,  with  the  double  movable  mires, 
or  hj  sliding  the  one  along  the  arc,  as  the  case 
may  be.  They  must  be  brought  close  enough,  un- 
til by  the  reflected  image  on  the  cornea,  they  ap- 
pear to  touch  each  other.  Now,  when  the  lines 
are  continuous  and  the  edge  of  the  mires  appear  to 
touch  each  other,  as  just  explained,  the  arc  is  said 
to  be  in  the  primary  position.  You  must  previous- 
ly have  drawn  the  telescope  as  far  from  the  pa- 
tient's eye  as  is  consistent  with  a  clear  and  dis- 
tinct view  of  the  central  images.  By  doing  this, 
the  i^eripheral  images  are  drawn  out  of  focus,  and 
will  appear  more  blurred.  Having  thus  secured 
the  continuation  of  the  lines  and  an  approxima- 
tion of  the  edges  of  the  mires,  we  note  the  angle  as 
marked  by  the  long  white  pointer,  previously 
mentioned  as  being  attached  to  the  center  of  the 
arc.  This  will  mark  for  us  the  angle  of  the  first, 
or  primary,  position. 

AYe  now  turn  the  telescope  with  its  arc  through 
90°,  -or  until  the  short  pointer  on  the  mire  occupies 
the  same  position  as  the  long  pointer  on  the  arc 
did,  before  rotating  it.  This  rotating  should  take 
place  from  left  to  right.  If  after  rotating  the  arc 
through  90°,  we  find  the  lines  on  the  mires  are  not 
exactly  continuous,  we  make  them  so  by  rotating 
the  arc  a  few  degrees  either  way.    Now,  if  the  eye 


102    REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

be  astigmatic,  the  mires  will  be  found  to  have  over- 
lapped each  other,  more  or  less,  according  to  the 
amount  of  astigmatism.  This  overlapping  of  the 
mires  is  shown  by  milky  whiteness  of  the  overlap- 
ping parts,  and  the  amount  of  astigmatism  is  cal- 
culated by  the  amount  of  overlapping,  the  overlap- 
ping of  each  step  on  the  mire  representing  one  di- 
optre of  astigmatism,  and  each  fraction  of  a  step 
the  fraction  of  a  dioptre. 

The  arc,  after  being  rotated  through  90°  as 
just  stated,  is  now  said  to  be  in  the  second  posi- 
tion, and  when  this  overlapping  takes  place,  either 
in  or  near  the  vertical  meridian,  the  astigmatism 
is  said  to  be  "according  to  the  rule,"  which  shows 
that  the  meridian  of  greatest  curvature  is  the  ver- 
tical or  near  the  vertical,  as  the  case  may  be;  and 
the  exact  point  is  noted  by  means  of  the  figures  on 
the  edge  of  the  disk,  as  pointed  out  to  us  either  by 
the  long  pointer  now  in  the  primary  position,  or 
the  short  pointer  on  the  mires  in  the  second  posi- 
tion, and  the  two  meridians  as  indicated  by  the 
long  and  short  pointers,  will  correspond  ex.actly 
with  the  meridians  of  greatest  and  least  curvature. 

In  some  cases,  as  you  turn  the  arc 
through  90°,  that  is,  from  the  primary  to  the  sec- 
ondary position,  you  will  find  that  the  mires,  in- 
stead of  overlapping,  are  separated  as  the  lines 
passing  through  them  become  continuous.    In  this 


OPHTHALMOMETRY.  103 

case,  the  astigmatism  is  said  to  be  "contrary  to  the 
rule,"  and  the  corneal  meridian  of  greatest  curva- 
ture is  horizontal  instead  of  vertical. 

To  measure  the  amount  of  the  astigmatism 
when  "contrary  to  the  rule,"  the  mires  had  better 
be  brought  together  while  the  arc  is  in  the  second 
position,  and  as  it  is  rotated  back  to  the  primary 
position,  through  90°,  the  amount  of  overlapping 
which  takes  place  can  be  noted,  as  in  the  former 
case,  and  the  degree  of  astigmatism  calculated  in 
the  same  manner.  After  completing  the-€xamina- 
tion  of  one  eye,  you  proceed  to  examine  the  other 
in  the  same  way,  making  whatever  change  is  ne- 
cessary in  the  position  of  the  instrument,  so  as  to 
get  a  clear  and  accurate  rellection  from  the  cornea. 

Q.  But  supposing  that  the  eye  under  exami- 
nation be  emmetropic,  and  not  the  seat  of  corneal 
astigmatism,  how  are  we  to  know  it  when  using 
the  ophthalmometer? 

A.  In  that  case,  after  placing  the  edges  of 
the  mires  together  and  rotating  the  arc  through 
90°,  or  a  quarter  of  a  circle,  you  will  observe  that 
there  will  be  no  overlapping  or  separating  of  the 
mires  as  there  is  in  astigmatism,  showing  that  the 
curvature  of  the  cornea  is  the  same  in  all  meridi- 
ans, hence  not  the  seat  of  astigmatism. 

Q.     But  supposing  that  the  eye  is  the  seat  of 


104    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

astigmatism,  how  are  Ave  to  know  whether  it  is  of 
the  hypermetropic  or  myopic  variety? 

A.  This  we  cannot  tell  by  means  of  the  oph- 
thalmometer, as  this  instrument  only  points  out  to 
us  the  meridians  of  greatest  and  least  curvature, 
and  the  particular  kind  of  astigmatism  resulting 
from  an  asymmetrical  condition  of  the  cornea, 
must  be  determined  by  some  of  the  auxiliary  tests. 

Q.  Does  the  ophthalmometer  always  give  the 
correct  amount  of  total  corneal  astigmatism? 

A.  It  does  not,  as  we  may  have  a  certain 
amount  of  lenticular  astigmatism  entering  into 
the  total  amount  of  astigmatism,  as  determined 
with  the  ophthalmometer. 

Q.  Is  there  any  rule  to  follow  in  regard  to 
taking  this  lenticular  astigmatism  into  considera- 
tion when  prescribing  correcting  cylinder  lens? 

A.  There  is  a  rule  formulated  by  Javal, 
which  consists  of  subtracting  .05D.  from  the  read- 
ing of  the  ophthalmometer  when  the  astigmatism 
is  "with  the  rule,"  and  adding  .05D.  when  the  as- 
tigmatism is  "contrary  to  the  rule."  This  rule  will 
be  found  sufSciently  accurate  in  a  large  number  of 
cases. 

The  utility  and  applicability  of  the  ophthal- 
mometer, as  you  see,  is  limited  to  the  determina- 
tion of  corneal  astigmatism.    While  we  cannot  ap- 


OPHTHALMOMETRY.  105 

ply  it  to  all  the  refractive  conditions  of  the  eye,  it 
will  be  found  a  very  serviceable  instrument  in 
those  cases  of  astigmatism  where  any  uncertainty 
exists  as  to  the  amount  of  and  also  as  to  the  axis 
of  the  correcting  cylinder  lens.  Its  use  will  also 
enable  us  to  forego  the  use  of  a  mydriatic  in  many 
cases,  thus  saving  the  patient  the  inconvenience  of 
undergoing  this  very  unpleasant  experience.  It 
will  also  be  found  a  valuable  time-saving  test,  as 
many  cases  otherwise  requiring  a  great  deal  of 
time  and  patience  can  be  readily  determined  by 
-the  use  of  the  ophthalmometer. 


CHAPTER  IX. 


Skiascopy,  Retinoscopy,  or  Shadow  Test. 

Q.  What  is  skiascopy,  Retinoscopy  or  the 
Shadow  test,  as  it  is  called? 

A.  It  is  a  method  of  determining  the  refrac- 
tive condition  of  the  eye  by  means  of  reflecting 
light  from  a  given  point  of  illumination,  on  to  the 
cornea  of  the  eye,  by  means  of  a  small  mirror 
called  the  retinoscope,  at  a  distance  of  forty  inches 
usually,  from  the  patient  and  watching  the 
movement  of  the  retinal  reflex,  as  it  is  made  to 
pass  over  the  pupillary  space,  by  causing  the  reti- 
noscopic  mirror  to  be  slightly  moved  from  side  to 
side,  or  up  and  down. 

Q.  What  kind  of  a  mirror  is  best  to  use  in 
this  work  of  retinoscopy? 

A.  That  is  largely  a  question  of  individual 
choice,  some  preferring  a  small  plain  mirror  with 
a  central  aperture,  or  one  from  which  the  silver 
has  been  removed  from  its  central  point,  while 
others  prefer  a  slightly  concave  mirror  with  a  focal 

106 


SKIASCOPY 


107 


point  of  S  inches  or  10  inches.    For  my  own  use,  I 
prefer  the  plain  mirror. 

Q.     What  are  your  reasons  for  preferring  the 
plain  retinoscopic  mirror? 

Figure  18. 


Plain  Mirror  Retinoscope. 

A.     Because  I  believe  it  is  much  easier  to  use, 
and  YOU  hare  only  to  note  the  direction  of  the 


108    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

movemeut  of  the  mirror  when  calculating  the  re- 
flction  from  the  retina,  while  with  the  concave 
mirror,  all  movements  of  the  mirror  are  reversed 
before  reaching  the  eye,  a  fact  you  must  always 
remember.  However,  there  are  some  advantages 
connected  with  the  use  of  the  concave  mirror, 
which  will  be  pointed  out  later  on. 

Q.  What  position  should  your  patient  occu- 
py in  relation  to  the  point  of  illumination? 

A.  With  the  plain  mirror,  the  light  should 
come  through  a  small  hole  made  in  a  cover  for  an 
ordinary  chimney  of  an  Argand  burner.  The  hole 
in  the  chimney  cover  should  be  opposite  the  bright- 
est part  of  the  flame.  The  hole  need  not  be  over 
three-quarters  of  an  inch  in  diameter,  as  it  is  eas- 
ier to  watch  the  reflex  from  a  pencil  of  light  than 
from  a  diffused  one.  If  you  wish  to  operate  at  a  dis- 
tance of  one  metre  from  your  patient, which  I  think 
is  the  best  plan,  you  must  have  the  light  close  to 
the  mirror,  as  the  distance  from  the  light  to  the 
mirror  must  count  in  your  metre's  distance  from 
your  patient,  the  same  as  if  the  light  came  from  a 
point  behind  the  mirror,  corresponding  in  distance 
from  the  light  to  the  mirror;  for  example,  if  your 
source  of  illumination  is  12  inches  from  your  mir- 
ror, you  must  consider  it  as  coming  a  distance  of  12 
inches  behind  the  mirror,  and  this  must  be  reck- 
oned in  your  metre's  distance  from  your  patient. 


SKIASCOPY.  109 

Q.  In  what  direction  should  your  patient 
look  when  using  the  retinoscope? 

A.  They  should  look  a  little  to  the  right 
when  examining  the  right  eye,  and  a  little  to  the 
left  when  the  left  is  being  examined.  This  is  in  or- 
der that  the  rays  entering  the  eye  may  pass  along 
the  visual  axis  of  the  eye,  and  strike  the  retina  at 
the  maculae  lutea,  or  "yellow  spot." 

Q,  How  are  we  to  determine  by  the  move- 
ment of  the  retinal  reflex  that  the  eye  is  ametropic? 

A.  By  observing  the  direction  in  which  the 
reflex  moves,  when  a  pencil  of  light  is  projected  on 
to  the  cornea,  and  by  slight  movement  of  the  mir- 
ror made  to  pass  to  and  fro  over  the  puiDillary 
sijace.  When  at  a  distance  of  40  inches  with  your 
plain  mirror,  you  will  observe  that  when  you  are 
examining  an  eye  that  is  emmetropic,  there  will  be 
little  or  no  movement  of  the  reflex  across  the  pu- 
pillary space  when  the  mirror  is  slightly  rotated. 
This  is  because  the  eye  being  emmetropic,  the  rays 
of  reflected  light  strike  the  dioptric  media  of  the 
eye  practically  parallel,  and  coming  to  a  focus  at  a 
point  on  the  retina,  corresi)onding  to  the  principal 
focal  distance  of  the  eye,  there  is  very  little,  or  no 
movement  over  the  pupil  as  the  mirror  is  slightly 
moved,  owing  to  there  being  little,  or  no  change  in 
the  point  of  illumination  on  the  retina. 


110    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Now  in  livpermetropia,  the  reflected  rays  are 
brought  to  an  indistinct  focus  on  the  retina,  in 
front  of  the  principal  focal  i)oint  of  the  eve,  hence 
the  retinal  illumination  is  greater  but  less  bril- 
liant, and  as  the  retinoscope  is  moved  on  its  axis, 
there  will  be  a  greater  excursion  of  the  retinal  il- 
lumination, and  as  it  is  reflected  back  by  the  reti- 
na through  the  dioptric  media,  there  will  be  no- 
ticed a  greater  activity  of  the  rays  as  they  move 
across  the  pupil,  and  the  movement  of  the  reflex 
will,  3^ou  will  observe,  be  in  the  same  direction  as 
the  movement  of  the  light  on  the  face,  and  also  in 
the  same  direction  as  the  movement  of  the  mirror, 
when  the  plain  mirror  is  used,  and  contrary  to  the 
movement  of  the  light  on  the  face  and  the  direction 
of  the  movement  of  the  mirror,  when  the  concave 
mirror  is  used. 

In  myopia,  there  will  be  a  movement  of  the 
reflex  observed  also,  as  in  hypermetropia,  but  with 
the  plain  mirror,  the  movement  will  be  against 
the  movement  of  the  light  on  the  face,  while  with 
the  concave  mirror  it  will  be  in  the  same  direction 
as  the  light  on  the  face,  and  likewise  in  the  same 
direction  as  the  movements  of  the  mirror.  For  this 
reason,  we  think  it  best  not  to  complicate  the  mat- 
ter more  than  necessary  in  our  descrijDtion,  and 
hence  we  will  imply  the  use  of  the  plain  mirror  in 
this  method  of  determining  the  different  refrac- 


SKIASCOPY.  Ill 

tive  conditions  by  means  of  retinoscopy.  After 
finding  out  the  direction  of  the  movements  of  the 
retinal  reflex  in  the  different  forms  of  ametropia, 
we  shall  now  proceed  to  explain  more  specially  the 
means  of  measuring  the  degree  of  ametropia  by 
this  method. 

In  hypermetropia,  we  have  previously  seen, 
the  rays  of  light  being  reflected  from  the  retina  of 
the  eye  through  the  dioptric  media,  diverge. 
These  diverging  emergent  rays  must  be  rendered 
parallel  before  entering  the  examiner's  eye, 
through  the  aperture  of  the  retinoscope.  This  par- 
allelism of  the  rays  is  brought  about  by  the  con- 
verging power  of  a  convex  lens  placed  close  to  the 
eye  of  the  patient,  in  a  suitable  pair  of  trial  or 
spectacle  frames,  and  the  convex  lens  that  stops 
the  reflex,  will  measure  the  amount  of  total  hyper- 
metropia ;  but  if  you  are  not  fully  satisfied,  you 
continue  to  increase  the  strength  of  the  convex 
lens  before  the  patient's  eye,  until  you  have  a  dis- 
tinct reversal  of  the  movements  of  the  retinal  re- 
flex, as  seen  at  your  distance  from  the  patient, 
namely,  40  inches,  and  this  glass,  minus  ID.,  will 
give  you  the  total  amount  of  hypermetropia.  For 
example,  supposing  that  in  looking  as  to  the  direc- 
tion of  the  retinal  reflex,  you  flnd  it  to  be  with  the 
movement  of  the  mirror,  and  in  order  to  stop  the 
motion  entirely,      it  will  require      a  convex  lens 


113    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

of  3D.,  but  with  any  stronger  lens,  it  produces  a  re- 
versal of  the  motion  of  the  retinal  reflex.  Well, 
for  iDarallel  rays,  this  reversal  point  at  40  inches 
distance  is  produced  by  a  convex  lens  of  ID.,  so  in 
order  to  determine  the  exact  amount  of  hyperme- 
tropia,  this  ID.  must  be  subtracted  from  the 
strength  of  the  lens  that  is  found  to  produce  a  re- 
versal, which,  in  this  case,  is  a  -!-3D.,  and  as  ID. 
from  3D.  leaves  a  difference  of  2D.,  this  represents 
the  amount  of  total  hypermetropia.  Now,  suppos- 
ing that  the  above  case,  instead  of  being  a  case  of 
simple  hypermetropia,  is  a  case  of  compound  hy- 
permetropic astigmatism.  Well,  in  this  condition, 
the  emergent  rays  are  divergent  in  both  meridians, 
but  more  divergent  in  one  meridian  than  the  oth- 
er; now,  in  the  meridian  of  greatest  divergence,  it 
will  take  a  stronger  convex  lens  to  stop  the  mo- 
tion, or  to  bring  about  the  reversal  point,  than  it 
will  in  the  other  meridian,  and  the  difference  in 
the  two  lenses  will  represent  the  amount  of  astig- 
matism. In  the  case  just  cited,  we  will  say  that  a 
reversal  of  the  motion  is  produced  by  a  convex 
lens  of  3D.  in  one  meridian,  while  it  requires  a  con- 
vex lens  of  •ID.  to  produce  a  reversal  in  the  other 
meridian  at  right  angles;  the  difference  in  these 
tAvo  lenses,  namely,  ID.,  will  represent  the  amount 
of  astigmatism.  This  we  will  say  something  more 
about  in  treating  of  the  several  specific  conditions 
of  refraction. 


SKIASCOPY.  113 

Q.  In  looking  at  the  moyement  of  the  reflex 
at  saj  40  inches,  you  find  the  action  of  the  reflex 
very  rapid,  and  the  illumination  of  the  pupillary 
space  very  great.    What  is  indicated  thereby? 

A.  A  low  degree  of  either  hypermetropia  or 
myopia,  according  to  the  direction  of  the  light  in 
the  pupillary  space;  that  is,  if  it  be  with  the  move- 
ment of  the  plain  mirror,  it  is  hypermetropia;  if 
against  the  movement  of  the  plain  mirror,  myopia. 

Q.  How  do  you  account  for  this  great  illum- 
ination of  the  pupil  and  the  rapidity  of  the  reflex 
action? 

A.  The  eye  being  but  slightly  ametropic,  the 
rays  are  brought  to  a  focus  on  a  small  portion  of 
the  retina,  near  the  principal  focal  point  of  the  eye. 
This  point  reflecting  back  all  the  light  with  great 
magnification,  accounts  for  the  bright  illumina- 
tion, while  the  magnification  of  the  slight  motion 
of  the  mirror,  accounts  for  the  rapidity  of  the  mo- 
tion seen  in  the  pupillary  space. 

Q.  When  observing  the  action  of  the  reflex 
from  this  same  distance,  that  is  40  inches,  and  the 
mo\  ements  seem  slow,  and  the  illumination  of  the 
pupillary  space  seems  dull,  what  is  indicated? 

A.  A  high  degree  of  ametropia,  either  hyper- 
metropia or  myopia,  according  to  the  movement 
either  with  or  against  the  light  on  the  face. 


114    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Q.     How  do  you  accouiit  for  this  i^eculiarity? 

A.  In  high  degrees  of  ametropia,  the  rays  do 
not  focus  on  the  retina  at  the  principal  focal  point 
of  the  eye,  hence  circles  of  diffusion  are  formed 
with  the  loss  of  a  large  part  of  the  light  thrown  in- 
to the  eye  by  the  mirror.  The  reflected  light  being 
diminished  by  the  diffusion  taking  iDlace,  less 
light  is  reflected  back  to  the  pupillary  space,  thus 
producing  a  dull  illumination.  This  dull  illumina- 
tion in  turn  renders  it  more  difficult  to  observe  the 
motion  of  the  reflex,  hence  its  apparent  slow  ac- 
tion. 

Q.  In  measuring  a  hypermetropic  eye  with 
the  retinoscope  and  convex  lens,  what  do  we  aim 
to  do? 

A.  To  produce  a  temporary  myopia  of  the 
patient's  eye. 

Q.     What  is  our  purpose  in  doing  this? 

A.  So  as  to  be  able  to  determine  the  exact 
"point  of  reversal." 

Q.  What  do  you  mean  by  the  "point  of  rever- 
sal?" 

A.  That  point  at  which  the  motion  of  the  re- 
tinal reflex  is  changed  from  one  direction  to  the 
opposite. 

Q.  Where  is  the  "point  of  reversal"  general- 
ly fixed  in  retinoscopic  examinations  of  the  eye? 


SKIASCOPY.  115 

A.  At  about  4.0  inches  from  the  examined 
e}'e,  or  at  about  the  point  at  which  the  examiner 
sits. 

Q.  Where  is  the  "point  of  reversal"  of  a  myo- 
pic eye  located? 

A.  At  its  punctum  remotum,  whatever  dis- 
tance this  may  be  from  the  eye. 

Q.  How  can  we  determine  between  an  em- 
metropic eye  and  a  low  degree  of  hypermetropia 
by  this  method? 

A.  We  have  seen  that  in  the  emmetropic  eye 
there  is  no  movement  of  the  retinal  reflex  in  the 
pupil.  Now",  if  we  pjace  a  convex  lens  of  one  di- 
optre before  this  e^'e,  we  produce  a  temj)orary  con- 
dition of  myopia  of  one  degree,  and  the  motion  of 
the  reflex  Avill  be  seen  to  move  against  the  move- 
ment of  the  light  on  the  face,  hence  we  conclude 
the  eye  is  emmetropic;  but,  if  we  have  a  hyperme- 
tropia of  low  degree,  say  .05  L).,  the  movement  of 
the  light  will  be  seen  to  be  with  the  light  on  the 
face,  or  with  the  movement  of  the  mirror;  but  if 
you  place  a  convex  lens  of  1  D.  before  the  eye,  you 
produce  a  myopia  of  .05  D.,  and  by  moving  further 
aAvay,  the  point  of  reversal  will  be  found  to  be  at 
about  80  inches  from  your  patient's  eye;  in  other 
words,  shoAving  a  myopia  of  half  a  dioptre,  but  as 
you  must  subtract  1.  D.  of  myopia,  caused  by  the 


116    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

use  of  3'oiir  convex  lens  of  1  D.,  from  this  condi- 
tion, you  will  see  you  have  as  a  result  a  liyperme- 
tropia  of  .05  D. 

Tliis  you  can  iH'ove  by  putting  a  convex  lens 
of  .05  D.  before  your  patient's  eye,  wlaen  you  will 
observe  all  the  movements  of  the  reflex  to  cease, 
this  being  brought  about  by  this  lens  bringing  the 
slightly  divergent  rays  of  the  eye  into  a  condition 
of  parallelism. 

The  amount  of  the  hypermetropia  is  deter- 
mined, as  we  have  seen,  by  the  convex  lens  neces- 
sary to  bring  about  a  reversal  of  the  movements  of 
the  reflex  at  a  point  10  inches,  or  1  D.  from  our  pa- 
tient. This  lens  minus  1  I),  will  give  us  the  total 
hypermetroi^ia. 

In  a  case  of  simple  hypermetropic  astigma- 
tism, one  meridian  emits  parallel  rays,  while  the 
other  emits  divergent  rays.  Now  in  the  emmetrop- 
ic meridian  there  will  be  no  movement  of  the  re- 
flex, while  in  the  hypermetropic  meridian  the 
movement  will  be  in  the  direction  with  the  light 
on  the  face,  and  the  convex  lens  necessary  to  stop 
this  movement  will  represent  the  amount  of  astig- 
matism. For  example,  supposing  that  in  the  ver- 
tical meridian  there  is  no  movement  of  the  reflex 
in  either  direction,  but  that  it  requires  a  convex 
spherical  lens  of  2D.  to  stop  the  retinal  reflex  in 


SKIASCOPY.  117 

the  horizontal  meridian,  then  this  lens  would  re- 
present the  amount  of  hypermetropic  astigmatism, 
tmd  the  correcting  cylinder  glass  would  be  a  con- 
vex cylinder  of  2  D.  with  its  axis  vertical  or  par- 
allel ^'ith  the  emmetropic  meridian. 

In  a  case  of  compound  hypermetropic  astig- 
matism, the  mov€*nient  of  the  reflex  will  be  with 
the  mirror  in  both  meridians,  but  it  will  require  a 
stronger  convex  lens  to  stop  them  in  one  meridian 
than  the  other,  and  the  difference  in  the  two  lens 
will  measure  the  amount  of  astigmatism.  For  ex- 
ample, if  we  have  a  case  in  which  the  movements 
are  stopped  in  the  vertical  meridian  with  a  convex 
glass  of  3  D.,  but  in  the  horizontal  meridian  it  re- 
quires a  convex  lens  of  4.50  D.,  then  the  difference 
in  the  two  lenses,  namely,  1.50  D.,  will  represent 
the  amount  of  astigmatism,  and  the  axis  of  the 
correcting  cylinder  must  be  placed  parallel  with 
the  meridian  of  least  ametropia,  or  in  the  vertical, 
and  we  would  have  as  a  correcting  combination 
the  following  formula : 

-1-3  D.  S.  C  -1-1:50  D.  Cyl.  A.x  90«. 

Xow  in  testing  myopic  conditions  with  the  re- 
thioscope,  all  we  have  to  do  is  to  substitute  the 
concave  lens  for  the  convex  before  the  patient's 
^ye,  and  also  the  remember  that  with  the  plain 
mirror  all  the  movements  of  the  retinal  reflex  are 


118    REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

against  the  movement  of  the  light  on  the  face,  as 
well  as  against  the  movements  of  the  mirror. 

^^e  can  in  a  general  way  estimate  the  strength 
of  the  redncing  lens  by  finding  ont  the  distance  of 
the  punctnm  remotum.  For  example,  if  this  be  20 
inches  from  the  eye,  then  we  will  need  a  lens  of 
2  D.  to  lender  the  converging  emerging  rays  of  the 
myopic  eye  parallel,  and  if  we  find  the  punctnm 
remotnin  at  10  inches  from  the  patient's  eye,  then 
it  will  require  a  lens  of  10  inches  focal,  or  4  D  con- 
cave, to  render  the  rays  parallel.  But  you  must  re- 
member that  ^\e  are  examining  the  eye  at  distance 
of  40  inches,  or  1  D.,  from  the  patient,  and  when 
we  find  a  glass  that  will  sufficiently  diverge  the 
emerging  converging  rays  to  bring  them  to  a  point 
at  10  inches,  or  to  cause  all  the  reflex  movement  to 
stop  at  this  point,  you  must  remember  that  you  are 
still  ID.  from  parallelism,  so  you  must  add  on  ID. 
to  the  concave  glass  before  the  eye,  in  order  to  esti- 
mate accurately  the  total  amount  of  myoiDia. 

For  example,  supposing  that  the  punctum  re- 
motum of  the  myopic  eye  is  at  10  inches,  it  will  re- 
quire a  concave  lens  of  1  D.  to  render  the  rays  par- 
all(^],  and  to  stop  all  retinal  reflex.  Xow  if  you 
were  examining  the  eye  from  infinity,  or  a  distance 
of  twenty  feet,  this  would  render  the  rays  of  light 
parallel,  and  at  this  point  of  twenty  feet  all  reflex 
would  stop;  but  as  you  are  situated  only  10  inches 


SKIASCOPY.  119 

from  your  patient,  all  it  will  require  to  bring  the 
reflex  to  a  standstill  at  this  point,  will  be  a  lens  of 
3D.,  but  in  estimating  the  total  amount  of  myopia, 
YOU  must  add  on  to  this  1  D.,  which  will  be  sufflci- 
cnt  to  change  the  rays  coming  from  the  eye  and 
converging  at  40  inches  to  a  condition  of  parallel- 
ism, or  if  you  are  at  a  point  nearer  than  40  inches 
to  your  patient,  say  28  inches,  or  about  1.50  D., 
then  you  must  add  this  on  to  the  concave  lens  that 
stops  the  retinal  reflex  at  this  point,  in  order  to  de- 
termine the  total  myopia. 

This  adding  to  in  myo'^iia  and  subtracting  in 
hyf>ermetropia,  have  led  many  to  fjrefer  to  observe 
the  letinal  reflex  from  a  distance  of  20  feet,  or  in- 
finity, and  this  is  a  simpler  way  than  any,  if  your 
room  and  light  will  permit  it,  in  that  case  you 
have  only  to  place  the  convex  lens  before  the  eye, 
that  stops  all  motion  at  this  point,  and  this  lens 
will  represent  the  total  hypermetropia,  and  the 
same  holds  good  in  myopia.  This  distance  also  en- 
ables you  to  locate  the  point  of  reversal  in  low  de- 
grees of  myopia  by  simply  approaching  your  i^ati- 
eut  until  this  point  is  found;  for  example,  if  it  is 
found  to  be  at  SO  inches  from  your  patient,  count- 
ing the  distance  from  the  patient's  e^'e  to  the  mir- 
ror, and  from  the  mirror  to  the  source  of  illumina- 
tion, in  this  estimation,  then  you  have  a  myopia  of 
.05  D.,  and  you  can  prove  it  by  placing  this  lens 


120    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

before  tlie  ere  when  the  rays  are  parallel,  and  there 
will  be  no  point  of  reversal,  but  if  you  increase  it 
you  will  create  a  temporary  hypermetropia  and 
the  motion  in  the  pupillary  space  will  again  be 
seen,  but  will  move  with  and  not  against  the  light 
on  the  face.  Owing  to  its  simplicity  this  method 
of  using  the  mirror  at  a  distance  of  20  feet  has 
many  advocates. 

Simple,  myopic  astigmatism  is  determined  by 
the  retinal  redex  moving  against  the  light  on  the 
face,  in  one  meridian  only,  while  in  the  other  me- 
ridian there  is  no  motion.  The  amount  of  astig- 
matism is  measured  by  the  concave  glass  neces- 
sary to  stop  the  motion  in  this  meridian.  For  ex- 
ample, if  the  mirror  shows  the  reflex  to  move  only 
in  one  meridian  and  the  movement  is  against  the 
movement  of  the' light  on  the  face,  then  you  have 
myopic  astigmatism,  and  if  it  requires  a  concave 
glass  of  one  and  a  half  dioptre  to  stop  this,  then  the 
amount  of  astigmatism  is  1.50  D.,  and  the  axis  of 
the  correcting  cylinder  must  be  put  at  right  angles 
to  the  myopic  meridian.  The  same  is  true,  also,  of 
compound  myopic  astigmatism.  You  must  test 
each  meridian  separately,  and  the  difference  in  the 
two  lenses  will  give  you  the  amount  of  astigma- 
tism, and  the  axis  of  the  correcting  cylinder  must 
be  at  right  angles  to  the  meridian  of  greatest  ame- 
tropia. 


SKIASCOPY.  121 

In  testing  for  mixed  astigmatism,  you  must 
also  test  each  meridian  separately.  The  hyperme- 
troi)ic  meridian  ujust  be  tested  with  a  convex 
lens,  while  the  myopic  meridian  must  be  measured 
by  means  of  a  concave  lens.  This  is  not  a  difficult 
matter  to  do,  and  with  a  little  practice  you  will  find 
the  retinoscope  a  valuable  adjunct  in  refractive 
work,  especially  for  young  children  or  illiterate 
persons. 

The  use  of  the  concave  retinoscope  mirror  is 
the  same  in  every  respect,  except  that  you  must 
remember  that  your  point  of  illumination  is  really 
in  front  of  the  mirror  at  its  focal  distance,  and  that 
all  the  movements  of  the  reflex  are  exactly  the  re- 
verse of  what  they  are  with  the  plain  mirror.  It  is 
not  so  necessary  to  cover  your  chimney  when  us- 
ing the  concave  mirror.  The  mirror  on  the  oph- 
thalmoscope will  answer  all  purposes  of  a  concave 
mirror  for  retinoscopic  work,  and  it  is  often  well 
to  observe  the  condition  of  the  reflex  with  it,  and 
familiarize  yourself  with  the  use  of  both.  The 
shape  of  the  retinal  reflex  also  throws  light  on  the 
variety  of  ametropia  we  have  to  deal  with;  in  sim- 
ple hypermetropia  or  myopia  it  is  circular  in  shajie, 
while  in  astigmatism  of  either  variety  it  is  more 
band-like,  or  ribbon-shaped. 

It  is  well  to  observe  all  these  little  details,  as 
they  will  all  contribute  their  own  share  in  assist- 
ing us  in  making  a  diagnosis  of  the  refractive  con- 
ditions of  the  eye  by  means  of  retinoscopy. 


CHAPTER  X 


Presbyopia, 

Q.     What  is  meaut  by  presbyopia? 

A.  It  means  that  change  which  takes  place 
in  most  eyes  at  a  certain  period  in  life,  when  the 
accommodation  of  the  eye  is  not  sufficiently  strong 
to  adjust  the  eye  for  close  work,  or  in  other  words, 
when  the  near  point  of  the  eye  has  receded  to  such 
a  distance  that  it  is  no  longer  possible  to  use  the 
eye  for  close  work,  with  comfort  or  ease. 

Q.  "When  does  this  change  in  the  accommo- 
dation of  the  eye  generally  take  place? 

A.  It  is  a  very  gradual  change  beginning  at 
about  the  age  of  ten  years,  and  gradually  increas- 
ing, until  at  about  the  age  of  seventy-three  years, 
's%]ien  it  is  complete.  When  presbyopia  is  fully 
and  comj)]etely  developed,  there  is  no  longer  any 
punctum  proximum,  or  near  point,  or  in  other 
words,  the  punctum  proximum  and  the  punctum 
remotum  become  the  same. 

Q.     What  is  the  cause  of  presbyopia? 

133 


PRESBYOPIA.  123 

A.  It  is  caused  by  the  crystalline  lens  of  the 
eye  becoming  hard,  so  that  the  action  of  the  ciliary 
muscle  is  no  longer  sufficient  to  increase  the  refrac- 
tive power  of  the  lens  by  increasing  its  curvature, 
which,  as  we  have  seen  in  a  preceding  chapter,  is 
necessary  to  see  near  objects  distinctly. 

This  is  a  slow  but  gradual  change,  and  we  do 
not,  as  a  rule,  suffer  any  inconvenience  from  it  un- 
til about  the  age  of  42  years,  when  the  near  point 
has  receded  from  the  eye  a  distance  of  40  c,  m.,  or 
about  IG  inches,  when  we  find  it  difficult  for  us  to 
see  distinctly  for  any  length  of  time  when  using 
our  eyes  for  close  work,  such  as  reading,  writing, 
etc.  This  change  takes  place  sometimes  earlier 
than  this  in  hypermetropia,  and  is  always  delayed 
to  a  much  later  period  in  myopes,  this  depending 
entirely  on  the  degree  of  myopia. 

Q.     How  do  you  correct  presbyopia? 

A.  By  the  use  of  convex  glasses  placed  before 
the  eye,  and  w^orn  when  using  the  eyes  for  close 
work. 

Q.    How  does  a  convex  lens  accomplish  this? 

A.  By  adding  refractive  power  to  the  dioptric 
media  of  the  eye,  in  this  way  compensating  for  the 
'oss  of  adjustability  on  the  part  of  the  crystalline 
lens. 


124    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Q.  How  do  we  determine  the  strength  of  the 
convex  lens  necessary  for  this  purpose? 

A.  By  finding  the  lens  necessary  to  bring 
back  the  punctum  proximum  of  the  eve  to  a  point 
sufficiently  close  to  the  eve,  to  enable  the  patient  to 
use  his  eyes  for  close  work  without  strain  or  fa- 
tigue. This  is  generally  at  a  point  12  inches  or  14 
inches  from  the  eye. 

Q.  Is  there  any  rule  to  go  by  in  prescribing 
convex  lens  for  presbyopia? 

A.  Yes.  There  is  a  general  rule  that  assists 
us  in  forming  some  idea  as  to  the  strength  of  the 
glass  necessary,  but  we  must  not  be  satisfied  with 
generalities,  so  we  must  test  each  eye  separately 
for  the  close  point.  However,  we  will  give  the  rule 
which  you  must  remember  is  for  emmetropia 
alone,  and  where  you  have  a  refractive  condition 
other  than  emmetropia,  this  must  be  corrected, 
and  the  eye  made  emmetropic  before  applying  the 
rule.  After  the  eye  is  rendered  emmetropic,  either 
by  nature  or  by  a  perfect  correction  of  the  ame- 
tropia, we  calculate  that  a  patient  45  years  old 
will  require  a  convex  lens  of  ID.  to  correct  his 
presbyopia;  that  at  50  years  old  they  will  require 
a  convex  lens  of  2  D.;  and  at  55  years  old,  will  re- 
quire one  of  2.50  D.,  while  at  60  years  old,  a  3  D. 
will  be  required;  but,  as  previously  stated,  this 


PRESBYOPIA.  125 

rule  is  only  approximately  correct,  and  each  case 
must  be  carefully  tested,  but  this  rule  with  a  given 
age,  will  aid  us  somewhat  in  our  calculation. 

Q.  Then  in  case  we  have  a  case  of  ametropia 
complicated  with  presbyopia,  how  do  we  proceed 
to  correct  the  presbyopia? 

A.  By  first  correcting  the  ametropia  in  the 
usual  manner,  by  means  of  the  Snellen  test  type, 
and  the  other  methods  enumerated;  but  in  order  to 
more  clearly  understand  it,  I  think  it  best  to  take 
up  each  case  of  ametropia  separately,  and  consid- 
er them  in  connection  with  presbyopia,  in  this  way 
giving  us  a  clearer  idea  as  to  how  each  case  is  to  be 
treated.  In  the  first  place  we  will  take  emmetrop- 
ia,  and  by  following  the  rule  given  above,  w^e  will 
be  able  to  readily  form  some  idea  as  to  the  convex 
lens  necessary  to  correct  a  given  case  of  presby- 
opia, by  finding  the  age  of  the  patient.  As  this  is 
the  very  simplest  form  of  presbyopia,  there  will  be 
found  no  trouble  in  correcting  it. 

Now,  in  case  our  patient  is  hypermetropic  and 
presbyopic  also,  we  first  proceed  to  correct  the  hy- 
permetropia,  and  after  having  done  this  satisfac- 
torily, we  proceed  to  correct  the  presbyopia.  For 
example,  we  have  a  patient  55  years  old,  who  has 
a  hypermetropia  of  1.50  D.  as  determined  in  the 
usual  manner.    This  lens  then  renders  him  emme- 


126     REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

tropic,  and  at  50  years  an  emmetrope  usually  re- 
quires a  convex  lens  of  2.50  D.  to  correct  his  pres- 
byopia, then  in  determining  the  glass  necessary, 
we  must  add  the  two  together,  and  we  find  that 
-fl.50  D.S.  added  to  a  -r-2.50  D.S.  equals  4  D.S.;  in 
other  words,  a  4  D.S.  or  alOinch  glass  will  be  neces- 
sary to  bring  his  close  point  near  enough  to  his 
eye  to  enable  him  to  use  them  with  any  degree  of 
comfort. 

This,  then,  is  a  case  of  simple  hypermetropia, 
with  presbyopia.  Xow,  in  case  we  have  a  case  of 
compound  hypermetropic  astigmatism,  we  proceed 
in  exactly  the  same  way;  that  is,  we  correct  the  dis- 
tant vision  in  the  usual  way  and  then  correct  the 
presbyoj)ia.  For  example,  if  v^e  have  a  case  of 
compound  hypermetropic  astigmatism  in  a  patient 
50  years  old,  requiring  the  following  correction  for 
his  distant  vision,  to  bring  it  up  to  the  standard  of 
U,  that  is,  a  4-  2.25  D.  S.  C  — 1.25  cyl.  ax.  90^,  we 
must  put  this  glass  and  the  one  that  at  his  age 
would  correct  his  presbyopia  if  he  were  emmetrop- 
ic, together  to  find  out  the  glass  he  would  need  for 
close  work.  At  50  years  the  presbyopia  generally 
amounts  to  2  D.,  so  in  that  case  we  would  have  the 
following  formula  for  reading  glasses:  -;-2  D.  S. 
added  to  -r  2.25  D.  S.  C  "h  1-25  cyl.  ax.  90°,  or  add- 
ed together  would  equal  a  -^  4.25  D.  S.  3  w.  -^  1.25 
cvl.  ax.  90°  for  reading.    The  cvlinder  gl^ass  alwavs 


PRESBYOPIA.  137 

remaining  as  you  find  it,  to  correct  the  distant 
vision. 

Now  in  case  we  Iiave  simple  hypermetropic 
astigmatism  to  deal  with,  then  you  simply  correct 
the  astigmatism  by  means  of  a  cylinder  lens  and 
add  to  it  the  convex  lens  necessary  to  correct  the 
presbyopia.  To  cite  a  case  again,  supposing  our 
patient  requires  a  -p  cyl.  of  1.50  D.  ax.  90°  to  cor- 
rect his  hypermetropic  astigmatism,  and  he  is  45 
years  old;  then  we  find  the  glass  he  would  need  for 
his  close  work  would  be  as  follows: -f-1  D.  S.^-I- 
1.50  D.  cyl.  ax.  90*^,  thus  giving  us  a  correction  for 
his  astigmatism  and  presbyopia;  but  this  glass 
could  only  be  used  for  close  work,  as  it  would  blur 
his  distant  vision,  and  strain  his  eye  if  used  for 
that  purpose. 

The  cases  that  will  call  for  some  little  care  in 
connection  with  this  condition  of  presbyopia  are 
cases  of  myopic  astigmatism.  Now  you  will  re- 
member that  in  myopic  astigmatism,  the  eye  is 
emmetropic  in  one  meridian  and  myopic  in  the 
other.  Of  course,  your  patient  will  not  get  presby- 
opic in  the  myopic  meridian  as  soon  as  he  does  in 
the  emmetropic.  Supposing  that  he  has  a  myopic 
astigmatism  of,  say  ID.,  and  that  he  is  45  years 
old ;  now  if  he  were  emmetropic,  he  would  need  a 
convex  spherical  lens  of  ID.  at  45;  t)ut  he  is  astig- 


128    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

matic,  and.  hence  he  is  at  45  presbyopic  ID.  in  the 
emmetropic  meridian, and  his  myopic  meridian  has 
reached  a  condition  of  emmetropia  on  its  way  to- 
wards presbyopia.  So  his  punctum  proximum  is 
all  right  for  this  myopic  meridian,  while  it  has 
receded,  in  the  emmetropic  meridian,  so  we  find  in 
order  to  bring  it  back  to  a  proper  distance  in  this 
meridian,  will  require  the  aid  of  a  glass  that  con- 
verges rays  in  one  meridian  only,  and,  of  course,  a 
cylinder,  as  we  have  said  before,  does  this,  so  we 
would  correct  his  presbyopia  by  prescribing  a  con- 
vex cylinder  lens  of  1  D.  with  its  axis  at  90°,  or  ver- 
tical, and  we  will  find  that  with  the  aid  of  this  lens 
he  can  see  distinctly  and  use  his  eyes  at  the  close 
point  without  trouble. 

In  cases  of  myopic  astigmatism,  you  must  put 
the  cylinder  glass  at  right  angles  to  correct  the 
presbyopia;  for  example,  if  you  have  a  case  of 
myopic  astigmatism  at  150°  in  the  right  eye,  and  at 
30°  in  the  left,  then  the  axis  of  the  convex  lens  to 
correct  the  presbyopia  would  be  at  30°  in  the  right 
eye,  and  150°  in  the  left. 

Let  us  take  the  above  case  of  myopic  astigma- 
tism just  cited,  and  say  the  man  is  60  years  old, 
then  he  will  be  presbyopic  in  both  meridians  of  his 
eye,  but  more  presbyopic  in  the  emmetropic  merid- 
ian than  in  the  myopic.    At  60  years,  we  find  that 


PRESBYOPIA.  129 

lie  will  require  a  convex  lens  of  3  D.  in  the  emme- 
tropic meridian,  and  a  convex  lens  of  2  D.  in  the 
myopic  meridian,  so  we  would  have  to  give  him 
the  following  glass:  --  2  D.  S.  C  -r  1  cyl.  ax.  90°, 
for  his  close  work,  while  for  his  distant  correction 
he  still  used  his  concave  cyl.  of  1  D.,  axis  at  180°. 
jS^ow,  as  we  have  seen,  myoi)ia  delays  the  oc- 
currence of  presbyopia,  it  will  be  well  to  see  how 
we  are  to  deal  with  cases  of  myopia  of  certain  de- 
grees, complicated  with  presbyopia.  We  find  that, 
generally  speaking,  a  person  having  a  myopia  of  1 
D.,  instead  of  needing  a  convex  lens  for  close  work 
at  the  age  of  from  45  to  48  years  of  1  D.,  as  do  per- 
sons with  an  emmetropic  eye,  they  are  generally 
not  obliged  to  wear  glasses  for  jjresbyopia  for 
about  five  years  later,  or  not  until  50,  or  there- 
abouts, and  one  with  a  myopia  of  2  D.,  not  until 
about  55  or  so,  will  they  need  a  convex  glass  for 
close  work,  though  it  is  often  necessary  to  reduce 
the  distance  glasses  1  or  2  D.  for  close  work,  a  my- 
ope of  6  D.  say,  will  require  a  —  4  D.  for  reading, 
and  a  myope  of  10  D.  would  probably  require  a  — 
6  or  —  8  D.,  Avhile  a  myope  of  from  16  to  20  D.  will 
require  a  reduction  generall}^  of  from  4  to  6  D.  for 
close  work,  as  these  strong  concave  glasses  cause 
too  great  a  divergency  of  the  rays,  causing  difficul- 
ty in  using  them  for  close  work.  We  have  told  you 
in  a  previous  part  of  this  work  that  the  accommo- 


130    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

elation  is  very  little  used  in  myopia,  and  it  is  a 
fact,  that,  supposedly  from  this  reason,  the  ciliary 
muscle  is  very  poorly  fleveloped  in  this  class  of 
persons. 

This  will  end  all  we  have  to  say  about  refrac- 
tion, or  refractive  errors,  and  their  correction,  but 
before  concluding  we  must  say  a  few  words  about 
asthenopia,  or  eye-strain,  as  a  result  of  insufficien- 
cy of  the  ocular  muscles,  and  point  out  the  indica- 
tions for  £'orrecting  them,  a  very  important  part  of 
the  work  met  with  in  this  line. 


CHAPTER  XI. 


3Iuscular  Asthenopia. 

Q.  What  is  meant  by  muscular  asthenopia? 
•  A.  It  means  asthenopia,  or  eve-strain,  caused 
by  some  disarrangement  in  the  associated  action 
of  the  muscles  attached  to  the  eve-ball;  that  is,  the 
ribbon-like  muscles,  known  as  the  four  recti,  or 
straight  muscles,  and  the  two  oblique,  which  move 
the  eye-balls  in  harmony,  so  that  the  image  from 
any  object  in  the  field  of  vision  is  brought  to  a  fo- 
cus on  corresponding  parts  of  the  retinae,  thus 
enabling  us  to  see  one  object  and  not  two.  This  is 
called  single  vision. 

Q.  When  this  condition  of  single  vision  is  not 
present,  owing  to  some  marked  muscular  defect  or 
from  paralysis  of  certain  muscles, what  is  it  called? 

A.  It  is  called  diplopia,  or  double  vision.  It 
is  caused  by  the  focus  of  the  image  in  the  field  of 
regard,  falling  on  dissimilar  parts  of  the  two  eyes, 
that  is,  parts  of  the  retina  in  each  eye,  not  corres- 
ponding to  each  other,  as  is  necessary  to  produce 
single  vision.    This  produces  a  separate  image  for 

131 


132    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

each  eve,  and  being  api^reciatecl  as  such,  we  see 
two  objects  instead  of  one;  each  image  seems  to 
come  from  different  points  in  the  field  of  vision. 

Q.  Is  it  possible  to  have  a  diplopia,  or  double 
vision,  with  one  e^^e  only? 

A,  It  is.  This  condition  is  called  monocular 
diplopia,  and  is  generally  due  to  irregular  astig- 
matism, caused  by  surgical  operation  on  the  corn- 
ea, injuries,  or  some  marked  difference  in  the  re- 
fractive condition  or  power  of  different  parts  of 
the  crystalline  lens  or  cornea. 

Q.  How  can  monocular  diplopia  be  induced 
temporarily? 

A.  By  holding  a  prism  before  the  eye  so  that 
some  of  the  rays  i^assing  into  the  eye  will  pass 
through  the  prism.  The  ones  not  passing  through 
the  prism  will  enter  the  eye  and  form  an  image  in 
the  proper  place,  while  the  rays  that  pass  through 
the  prism  are  deflected  toward  the  perpendicular 
of  the  prism,  and  striking  the  retina  at  a  different 
part  will  form  a  separate  image,  thus  giving  rise 
to  the  formation  of  two  separate  images  which  are 
seen  and  appreciated  as  such. 

Q.  Do  all  cases  of  muscular  insufficiency,  as 
it  is  called,  produce  binocular  diplopia? 

A.  The  great  ma^rity  of  the  cases  of  muscle 
trouble  does  not.    The  muscular  deficiency  does 


MUSCULAR  ASTHENOPIA.  133 

not  allow  sufficient  disassociation  of  the  move- 
ments of  the  eye  to  cause  diplopia,  but  requires  an 
extra  amount  of  work  on  the  part  of  the  muscles 
to  keep  up  a  condition  of  affairs  b}'  which  single 
vision  is  maintained,  hence  the  asthenof)ia,  or  e^'e- 
strain,  resulting  from  this  constant  effort  to  main- 
tain muscular  equilibrium. 

Q.  But  whv  is  this  condition  of  single  vision 
maintained,  when  it  requires  such  an  effort  on  the 
part  of  the  muscles? 

A.  Because  for  some  inherent  reason,  on  the 
part  of  the  eyes,  double  vision  is  disagreeable  to 
them,  and  great  effort  is  made  on  their  part  to  pre- 
vent it,  consequently  when  this  condition  of  diplo- 
pia becomes  inevitable,  the  muscles  of  the  eyes  im- 
mediately exert  their  entire  muscular  power  to 
prevent  it,  by  so  turning  the  eye  as  to  bring  the 
rays,  striking  the  two  e^es,  to  a  focus  at  corres- 
ponding parts  of  the  retinae,  thus  enabling  us  to 
see  a  single  image  and  not  t^o  separate  images,  as 
would  be  the  result  if  the  focus  reached  the  retinae 
at  any  other  point  or  i)art,  a  very  unpleasant  and 
bewildering  sensation,  as  any  one  ever  suffering 
from  it  can  testify. 

Q.  Is  this  muscular  difficulty  confined  to  any 
particular  muscle  or  set  of  muscles? 


134    REFRACTIVE  AND  OPHTHALMIC  CATECHISM 

A.  xso;  the  trouble  may  exist  in  any  one,  or 
in  any  set  of  them. 

Q.  In  a  ease  of  asthenopia,  hoAv  are  we  to  de- 
termine that  the  fault  lies  in  the  muscles  of  the 
eye? 

A.  By  excluding  and  differentiating  it  from 
other  causes  of  asthenopia,  by  measuring  the 
strength  of  the  different  muscles  and  comparing 
the  result  with  that  of  normal  eyes. 

Q.     How  are  these  measurements  made? 

A.  Principally  by  inducing  a  temporary  con- 
dition of  dii3loj)ia,  by  the  use  of  prisms.  This  the 
eyes  will  resist  to  their  full  power.  This  strength 
as  measured  by  the  degrees  on  the  prism  will  re- 
present the  dynamic  power  of  the  eye  muscles. 
This  is  done  by  i)lacing  a  prism  of  a  given  strength 
with  its  apex  over  the  muscle  to  be  measured.  For 
example,  if  you  wish  to  test  the  adducting  power 
of  the  eye  or  their  power  to  roll  inward,  you  hold  a 
prism  with  its  apex  over  the  insertion  of  the  inter- 
nal recti,  and  when  the  eyes  fail  to  blend  the  two 
images,  the  limit  is  reached,  and  the  number  on 
the  prism  will  express  this  in  degrees. 

If  you  wish  to  measure  the  abductive  power  of 
the  eye,  you  do  so  by  placing  the  apex  of  the  prism 
over  the  insertion  of  the  external  recti.    The  cir- 


MUSCULAR  ASTHENOPIA.  135 

ciimcl action  is  determined  by  holding  the  prism 
before  the  eye  with  the  apex  over  the  insertion  of 
the  superior  or  inferior  recti,  it  does  not  matter 
which. 

To  be  more  explicit,  we  will  take  a  case  and 
test  it  in  the  usual  manner  of  conducting  one  of 
theses  tests  in  our  office.  The  room  is  slightly 
darkened,  and  a  lighted  candle  is  placed  on  a 
stand  at  a  distance  of  twenty  feet  and  on  a  level 
with  the  eyes.  The  trial  frame  is  placed  on  the 
patient,  and  it  is  better  to  place  the  red  glass  be- 
fore one  of  the  eyes,  while  conducting  this  exami- 
nation, as  it  renders  the  double  images  more  dis- 
tinct by  the  contrast  in  color. 

We  will  first  proceed  to  examine  the  internal 
recti  by  placing  a  prism  in  the  trial  frame,  or  hold- 
ing it  before  the  eye  with  its  apex  in  or  towards 
the  nose.  From  30°  to  40°  is  said  to  be  the  normal 
abductive  power  of  a  normal  eye,  that  is,  an  eye 
with  normal  muscular  power  ought  to  bring  the 
images  together  and  maintain  single  vision  even 
with  this  prism  before  one  eye,  or  preferably  the 
power  of  the  prism,  divided  equally  between  the 
tAvo  eyes.  But,  if  we  find  that  a  prism,  of  say  10°, 
before  the  eyes  with  the  apex  in  or  toward  the 
nose,  there  are  two  lights,  one  red  and  the  other 
white;  then  we  have  weak  adduction  of  10°,  in- 
stead of  30°  or  40°,  as  it  should  be. 


136    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Xow  in  the  same  wa}'  we  test  the  external 
miiscJes  and  we  find  that  the  abductive  power  is 
(jo  QY  8^,  or  normal,  then  we  can  at  least  i)resume  a 
lack  of  equilibrium.  The  mechanical  explanation 
of  this  is  quite  simple.  By  the  refractive  action  of 
the  prism,  the  rays  of  light  are  bent  towards  the 
base  and  tend  to  form  a  separate  image  for  the  eye 
over  which  it  is  placed,  at  a  point  of  the  retina  not 
corresponding  with  the  place  at  which  the  image 
is  formed  on  the  retina  of  the  other  eye.  The  dou- 
ble image  being  disagreeable  to  the  eye,  there  is  a 
nervous  stimulus  sent  out  at  once  to  overcome  this 
by  rolling  the  eye-ball  into  such  a  position  as  will 
bring  the  image  on  corresponding  parts  of  the  re- 
tinae. This  the  eye  succeeds  in  doing  up  to  a  cer- 
tain point,  which  by  using  prisms  of  increasing 
strength,  is  soon  discovered.  When  a  point  is 
reached  when  the  eyes  can  no  longer  fuse  the  im- 
ages, and  there  is  for  the  time  being  two  images 
instead  of  one;  the  limit  of  the  muscular  power  of 
the  eye  is  reached,  and  this  is  measured  by  the 
prism  necessary  to  bring  about  this  condition  in 
degrees. 

Any  great  amount  of  deviation  from  the  fig- 
ures taken  as  a  standard  of  normal  muscular  pow- 
er is  at  least  presumptive  evidence  of  a  lack  of 
muscular  equilibrium.     The  standard  for  the  ver- 


MUSCULAR  ASTHENOPIA.  137 

tical  muscles,  or  the  superior  and  inferior  recti,  is 
about  30.  There  may  also  be  a  general  weakness 
of  all  the  ocular  muscles,  so  that  separate  tests 
will  show  them  to  be  all  below  the  standard;  but 
still  there  may  be  no  loss  of  equilibrium;  however, 
this  is  best  determined  by  other  means  which  we 
shall  proceed  to  describe. 

The  test  for  muscular  equilibrium  is  best  de- 
termined by  producing  vertical  diplopia  by  means 
of  a  10°  prism,  before  one  eye,  base  up  or  down, 
with  the  red  glass  before  the  other  eye,  the  patient 
is  directed  to  look  at  the  candle  twenty  feet  away, 
as  before.  Instead  of  one  light,  he  will  see  two, 
one  above  the  other,  and  if  the  muscles  are  well 
balanced,  the  lights  will  be  in  a  vertical  line;  but 
if  not,  they  will  stand  out  at  either  side  of  a  verti- 
cal' line.  If  the  red  light  is  over  the  right  eye,  and 
the  red  image  stands  on  the  same  side  as  the  red 
glass,  there  is  said  to  be  homonymous  diplopia, 
and  this  is  caused  by  a  weakness  of  the  external 
recti;  but  if  the  red  light  is  seen  on  the  other  side, 
or  on  the  side  of  the  vertical  line  corresponding  to 
the  eye,  that  is,  not  covered  with  the  red  glass,then 
the  diplopia  is  said  to  be  crossed,  and  this  we  find 
is  due  to  muscular  insufficiency  of  the  internal 
recti. 

Q.    What  system  of  nomenclature  has   been 


138    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

adopted  to   designate    the    different    deviations 
wliich  the  eve  tends  to  assume? 

A.  A  system  formulated  by  Dr.  George  A. 
Stevens  of  New  York  city,  and  which  is  as  follows: 

When  the  eye  tends  to  turn  in  from  the  visual 
line,  it  is  called  esophoria.  When  the  eye  tends  to 
turn  out  from  the  visual  line,  it  is  called  exophoria; 
and  when  it  tends  to  turn  up  or  down  from  the  vis- 
ual line,  it  is  called  hyperphoria,  right  or  left,  as 
the  case  may  be.  We  may  have  a  combination  of 
these  conditions,  such  as  a  turning  in  and  up, 
when  it  is  called  hypo-esophoria,  while  if  it  turns 
out  and  up,  it  is  called  hypo-exophoria,  etc. 

The  amount  of  these  deviations  is  measured 
by  the  prism  necessary  to  restore  them  to  their 
normal,  or  what  may  be  designated  as  their  prim- 
ary position.  For  example,  if  in  examining  the 
eyes  in  this  way,  with  the  prism  over  the  left  eye 
and  the  red  glass  over  the  right,  we  find  the  red 
light  on  the  right  side  of  a  vertical  line,  and  it  re- 
quires a  prism  of  3°,  with  the  base  over  the  exter- 
nal recti,  to  bring  the  red  light  in  line  with  the  oth- 
ers, the  case  would  be  one  of  esoi)horia,  or  a  ten- 
dency to  turn  in  of  3°,  and  in  correcting  it  with 
prism,  the  base  must  be  placed  over  the  weak  mus- 
cles, or  out;  or  in  case  cutting  the  muscles  is  neces- 


MUSCULAR  ASTHENOPIA.  139 

sary,  or  a  tenotomy,  as  it  is  called,  it  must  be  per- 
formed on  the  internal  recti. 

Now  supposing  the  red  light  is  on  the  other 
side  of  a  vertical  line;  or,  that  we  have  crossed  di- 
plopia, and  that  it  requires  a  prism  of  4°  with  the 
base  in  or  over  the  internal  recti,  then  we  liave  a 
case  of  turning  out  of  tlie  eye-balls,  or  exophoria, 
as  it  is  called,  of  4°,  and  must  be  corrected,  either 
by  a  tenotomy  of  the  external  recti,  or  by  means  of 
a  prism  worn  with  its  base  in  or  towards  the  inser- 
tion of  the  weak  muscles.  Hypo-phoria  is  deter- 
mined and  measured. in  the  same  way,  using,  how- 
ever, an  imaginary  horizontal,  instead  of  a  vertical 
line.  These  tests,  however,  measure  only  the  man- 
ifest amount  of  trouble,  and  a  great  deal  of  latent 
trouble  may  be  discovered  after  correcting  the 
manifest  deficiency. 

It  is  in  these  cases  in  which  by  the  superior,  or 
excessive,  power  of  a  muscle  or  a  set  of  muscles, 
there  is  a  tendency  of  the  eye  to  deviate  from  the 
visual  axis,  and  in  which  there  is  an  effort  on  the 
part  of  the  weak,  or  opposing  muscles  to  overcome 
this  tendency,  that  asthenopia,  or  eye-strain,  re- 
sults, as  well  as  many  other  nervous  manifestations 
found  associated  with  it,  for  the  relief  of  which 
the  physician  is  put  to  the  greatest  tests  many 
times,  though  we  are   often  able  to   relieve  this 


140    REFRACTIVE  AND  OPHTHALMIC  CATECHISM.  ■ 

class  of  cases  to  a  very  marked  extent,  by  the  cut- 
ting of  a  muscle,  or  the  application  of  a  suitable 
prism. 

I  am  firmly  convinced  in  the  opinion  that  the 
greatest  amount  of  good,  in  the  greatest  number 
of  cases,  is  to  be  obtained  by  the  use  of  correcting 
prisms. 

Q.  What  is  the  condition  called,  according  to 
the  Stevens'  system  of  nomenclature,  when  the 
muscles  are  properly  balanced  and  no  loss  of  equil- 
ibrium is  found  to  exist? 

A.  Orthophoria,  or  a  condition  of  equilibri- 
um, or  as  he  defines  it,  "the  ideal  form  of  adjust- 
ment.'' 

Q.  When  the  various  deviations  are  taken  as 
a  whole,  what  is  it  called? 

A.  Heterophoria,  of  which  esophoria,  exo- 
phoria,  and  hyperphoria  are  varieties. 

Q.  Are  there  any  other  tests  for  these  condi- 
tions besides  the  trial  frame  test  spoken  of? 

A.  Yes,  there  are  several  other  tests  and  in- 
struments for  this  purpose,  chief  among  which  is 
the  Stevens'  phorometer,  as  well  as  other  forms  of 
the  same  instrument.  Then  there  is  the  Maddock 
rod  test,  the  Maddock  double-prism  test,  and  Stev- 


MUSCULAR  ASTHENOPIA. 


141 


Figure  19. 
Steven's  Phorometer,  with  Rotatikg  Prisms. 


For  Directions  see  other  side. 


142     REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Directions. 

The  phorometer  should  be  so  placed  that  the  side  of  the  slide  on 
which  the  scale  of  degrees  are  seen  should  be  from  the  patient. 
The  side  mark  R.  H.  and  L.  H.  will  then  be  before  the  patient's 
right  eye,  and  that  marked  E.  S.  and  E.  X.  before  the  left  eye. 
The  arm  of  the  instrument  is  to  be  brought  to  a  perfect  level,  as 
indicated  by  the  spirit  level.  To  determine  hyperphoria,  the 
instrument  being  adjusted  to  the  hight  of  the  patient's  eyes  and  at 
least  four  inches  in  front  of  them,  bring  the  level  of  the  prism  slide 
to  the  vertical  position.  The  pointer  will  then  be  at  O.  The 
patient  looking  through  the  two  glasses  at  an  object  (a  lighted  can- 
dle) placed  at  a  distance  of  twenty  feet  directly  in  front,  sees  double 
images  of  the  object.  Should  one  ot  the  images  appear  higher  than 
the  othpr,  the  prisms  are  caused  to  rotate  until  the  images  are 
brought  to  the  same  horizontal  plane.  By  making  the  rotation 
slowly  it  will  in  many  instances  be  carried  further  than  when  the 
correction  is  quickly  made.  The  pointer  then  indicates  the  form 
and  degree  of  manifest  hyperphoria. 

To  examine  Esophoria  and  Exophoria,  bring  the  lever  to  the 
horizontal  position  and  then  make  adjustments  until  the  images  are 
in  an  exact  vertical  line. 

ens'  stenopaeic  lens  test.  They  are  all  based  on 
the  same  principle  of  producing  contrasting  im- 
ages for  the  two  eyes,  and  a  description  of  each 
separately  we  do  not  deem  necessary  in  a  work  of 
this  kind.  I  am  a  little  partial  to  the  double-prism 
test  of  Maddock  when  testing  the  horizontal  mus- 
cles, and  it  is  an  easy  matter  to  determine  with  it 
the  manifest  esophoria  or  exophoria.  You  cannot 
use  it,  however,  so  well  with  the  vertical  muscles, 
and  the  rod  test  will  answer  very  nicely  for  this 
purpose,  as  it  will  also  for  the  horizontal  muscles. 
I  am  of  the  opinion  that  in  examining  this  class  of 


MUSCULAR  ASTHENOPIA.  143 

cases,  one  should  use  several  of  the  tests,  as  you 
cannot  always  depend  on  the  result  of  any  single 
one  of  them  alone. 

Figure  20. 


Maddox's  Test  for  Heterophoria 

Consists  of  a  hard  rubber  dise  mounted  in  a  metal  rim  of  the 
size  of  trial  lenses,  so  as  to  fit  easily  into  the  trial  frame,  which 
holds  in  the  center  a  glass  rod. 

The  effect  of  this  transparent  cj'linder  is  to  cause  an  apparent 
elongation  of  a  single  flame  into  a  thin  line  of  light,  quite  dissimilar 
from  the  flame  itself,  as  seen  at  the  same  time  Tvith  the  other  eye,  so 
that  there  remains  practically  no  desire  to  unite  the  two  images, 
whose  relative  position  thus  easily  indicates  the  condition  of  equilib- 
rium of  the  two  eyes.  This  is  always  at  right  angles  to  the  axis  of 
the  rod,  so  that  to  produce  a  vertical  line,  with  which  to  test  hori- 
zontal deviations,  the  rod  is  placed  horizontally,  and  to  produce  a 
horizontal  line,  to  test  vertical  deviations,  it  is  placed  vertically. 
The  test  is  made  prettier  and  any  desire  for  single  vision  still  further 
reduced  by  placing  a  red  glass  before  the  other  eye. 

Q.    Why  is  it  that  persons   suffering  from 
strabismus,  or  squint,  are  not  usually  so  unpleas- 


144    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

antly  affected  by  the  muscular  derangement  of  the 
eyes? 

A.  Because  the  rotation  of  the  eyes  in  these 
cases  is,  as  a  general  rule,  so  well-marked,  and  of 
such  a  positive  character,  that  there  is  little  or  no 
effort  on  the  part  of  the  eyes  to  blend  the  images, 
thus  producing  single  vision,  and  in  consequence 
of  this,  there  is  a  suppression  of  the  image  of  one 
of  the  eyes,  generally  the  non-flxing  eye,  or  the  eye 
that  squints  the  most.  There  being  no  effort  on 
the  part  of  the  eye  to  bring  the  images  at  corres- 
ponding parts  of  the  retinae,  there  is  no  strain  re- 
sulting, and  consequently  no  appreciable  effect 
produced. 

This  non-use  of  one  of  the  squinting  eyes,  in 
cases  of  marked  strabismus,  is  generally  the  cause 
of  the  poor  sight  usually  found  to  exist  in  one  eye, 
in  these  cases. 

Eye-strain  is  to  be  found  in  cases  where  the 
deviation  is  but  slight,  and  when,  by  an  extraordi- 
nary effort  on  the  part  of  the  muscles,  double  vis- 
ion, or  diplopia,  is  overcome;  but  usually  produc- 
ing asthenopia  by  this  extreme  effort.  Hence  it  is 
that  these  latter  cases  must  be  looked  after  and 
corrected,  when  a  case  of  decided  deviation, 
amounting  to  internal  or  external  strabismus,  will 
give  little  or  no  trouble,   except  in  reducing  the 


MUSCULAR  ASTHENOPIA.  145 

vision  in  one  eye,  generally  to  a  point  of  absolute 
uselessness,  a  condition  called  amblyopia  ex- 
anoi^sia,  and  which  is  thought  by  many  to  be 
caused  by  a  prolonged  continuous  suppression  of 
one  of  the  retinal  images,  while  many  others  think 
it  is  caused  by  a  condition  of  congenital  non-devel- 
opment of  the  eye,  and  that  there  being  no  instinct 
on  the  part  of  the  eye  to  maintain  a  certain  relation 
with  the  visual  axis  of  the  other  eye,  that  it  grad- 
ually turns  in,  as  a  result  of  the  preponderating 
influence  or  power  of  the  internal  rectus,  a  very 
nice  theory,  indeed,  and  x)artly  borne  out  by  the 
fact  that  we  rarely  find  this  condition  to  exist  in 
cases  of  external  strabismus,  or  outward  deviation 
of  the  eyes. 

Another  fact  that  may  have  some  bearing  as 
to  the  cause  of  this  amblyopia  ex-anopsia,  is  that 
in  most  cases  where  it  occurs,  the  eyes  are  gener- 
ally hypermetropic,  and  the  one  that  turns  in,most 
generally  very  much  so,as  this  is  regarded  as  a  non- 
developed  condition,  it  is  reasonable  at  least  to 
suppose  that  there  may  be  some  relationship  ex- 
isting between  the  two  conditions. 

Q.  Are  these  cases  of  heterophoria  always 
confined  to  one  variety  of  it? 

A.  No;  there  may  be  two  varieties  of  it  com- 
bined.   For  example,  we  may  have  a  case  of  right 


146    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

or  left  hy])erphoria  with  esophoria,  constituting 
what  is  called  hyper-esophoria;  or  we  may  have  a 
case  of  right  or  left  hyperphoria  combined  with 
exophoria,  giving  rise  to  what  is  designated  hyper- 
exophoria,  etc. 

There  are  also  subdivisions  of  these  varieties, 
with  -svhich  it  is  not  necessary  for  us  to  deal,  as  I 
believe  them  to  be  more  theoretical  than  practical 
in  their  applications. 

Q.  Is  there  always  found  a  lack  of  converg- 
ing power  for  close  work  where  there  is  found  an 
exophoria,  for  distance? 

A.  Not  always.  They  may  or  may  not  be 
connected.  It  is,  however,  always  best  to  test  the 
converging  power  of  the  eyes  for  a  close  point. 
This  can  be  done  by  holding  an  object,  such  as  a 
lead  pencil,  before  the  eyes,  and  ask  your  patient 
to  keep  his  eyes  fixed  on  it,  as  you  slowly  approach 
the  eye.  The  converging  power  can  in  this  way  be 
noted,  and  any  deficiency  can  be  readily  observed 
by  the  slow,  sluggish  way  in  which  one  or  both 
eyes  will  act  as  the  pencil  is  slowly  brought  to  a 
point  close  to  them.  The  two  eyes  will  follow  the 
pencil  until  it  reaches  a  certain  point,  when  it  is 
no  longer  possible  for  the  two  eyes  to  converge 
to  a  closer  point.    When  this  point  is  reached,  ei- 


MUSCULAR  ASTHENOPIA.  147 

ther  or  both  eyes  will  give  up,  as  it  were,  and  rotate 
outward. 

Many  of  these  cases  will  require  prismatic 
lenses  for  close  work,  while  many  of  them  are 
greatly  improved  by  the  systematic  exercise  of 
these  muscles,  either  with  prism  or  b}^  trying  for  a 
few  minutes  each  day,  to  converge  to  a  close  i)oint. 
For  this  purpose,  the  finger  or  a  lead  pencil  will 
answer. 

Q.  In  case  diplopia,  or  muscular  insufiflciency, 
is  caused  either  by  complete  or  partial  paralysis 
of  the  muscles,  are  these  same  measures  available? 

A.  The  exercise  is  good  for  this  condition,  but 
we  must  try  and  restore  the  muscles  to  their 
proper  tone,  by  the  internal  administration  of 
medicines,  and  by  the  application  of  electricity, 
before  we  can  hope  to  restore  harmonious  muscu- 
lar association  with  a  proper  restoration  of  the 
equilibrium. 

There  is  a  large  field  for  persevering  and  intel- 
ligent labor  in  the  domain  of  muscular  insufficien- 
cy, and  many  of  our  most  intractable  cases  will  be 
found  to  result  from  this  cause.  There  is,  like  in 
all  other  branches  of  scientific  investigation,  an 
honest  difference  of  opinion  as  to  the  relative  fre- 
quency and  aeteological  significance  of  this  class  of 


148    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

cases,  but  speaking  alone  from  the  standpoint  of 
personal  experience,  I  am  satisfied  that  the  cause 
of  many  of  the  cases  of  headache  and  other  nervous 
manifestations  that  we  meet  with,  is  to  be  found 
in  the  muscles  of  the  eye. 


MUSCULAR  ASTHENOPIA. 


149 


Figure  21. 
The  Dr.  Harold  Wilson  Phorometer. 


THE    WILSON    PHOROMETER. 

More  attention  is  paid  to  muscle  testing  to-day  than  ever  before. 
Many  eyes  seeminglj^  impossible  to  fit,  are  easily  corrected  Avlien 
the  condition  of  the  muscles  are  understood.  The  most  practical 
instrument  for  muscle  testing  (and  an  instrument  is  always  infinitely 
superior  to  a  trial  frame  and  prisms)  is  the  Dr,  Harold  Wilson  phor- 
ometer. 

The  large  disc  (see  illustration)  contains  a  Savage  double  prism, 
a  strong  Maddox  cylinder,  a  15  degree  prism  and  a  10  degree  prism 
— one  base  in,  the  other  base  out.  These  form  practically  the  only 
standard  muscle  tests,  and,  arranged  as  they  are  in  this  instrument, 
may  be  used  successively  and  quickly,  one  result  proving  the  other, 
thus  insuring  an  accurate  test  in  the  shortest  possible  time.  The 
disc  also  contains  one  blank  hole,  in  front  of  which  may  be  placed 
(in  a  clip  provided)  any  lens  desired  for  a  supplementary  test. 

A  set  of  revolving  prisms,  obtaining  any  value  up  to  10  degrees 
to  a  hairlike  nicety  by  a  rotating  pinion,  are  provided  for  the  test- 
ing.    They  are  almost  invaluable  for  exercising  the  muscles. 

The  Dr.  Harold  Wilson  Phorometer  is  the  only  instrument 
capable  of  testing  the  oblique  muscles  or  of  performing  a  complete 
instrumental  muscle  test. 

Made  by  E.  Kirstein  &  Sons  Co.,  Rochester,  N.  Y. 


CHAPTER  XII. 


Perimetry. 

Q.  What  is  perimetry,  and  what  is  it  princi- 
pally used  for? 

A.  It  is  a  method  used  for  the  purpose  of  de- 
termininji;  the  visual  acuity  of  different  parts  of 
tlie  retina,  to  determine  its  limitation  in  the  differ- 
ent meridians,  or  in  other  words,  to  measure  the 
"field  of  vision,"  which  is  that  part  of  space  which 
is  perceived  by  an  eye,  when  maintained  in  a  posi- 
tion of  central  fixation,  simultaneously  in  differ- 
ent directions. 

It  is  principally  used  for  the  purpose  of  draw- 
ing comparisons  between  the  field  of  vision  found 
to  exist  in  a  normal  emmetropic  eye,  and  one  the 
seat  of  pathological  change.  Diseased  conditions 
of  the  brain,  of  the  optic  nerve,  of  the  retina,  and 
many  other  parts  directly  or  indirectly  connected 
with  the  visual  apparatus,  may  be  the  means  of 
producing  material  change  in  the  perceptive  pow- 
er of  the  eye,  and  it  is  for  the  purpose  of  diagnosing 
these  changed  conditions,  that  the  perimeter  is  so 
frequently  used. 

150 


PERIMETRY.  151 

Q.  What  standard  of  visual  perception  is 
taken  as  a  basis  of  calculation  in  these  measure- 
ments? 

A.  The  visual  perception  of  a  healthy  normal 
emmetropic  eye,  for  different  colors,  in  different 
meridians.  The  perception  of  the  eye  varies  for 
different  colors.  It  is  greatest  for  white;  hence 
this  color  is  used  more  than  any  other  in  deter- 
mining its  perception.  The  perception  of  a  normal 
eye  is  as  follows  for  white:  For  the  right  eye,  to 
the  temporal  side  of  the  horizontal  meridian,  90°, 
or  more;  to  the  nasal  side  of  the  horizontal  merid- 
ian, 60°;  the  upper  part  of  the  vertical  meridian, 
about  55°;  while  for  the  lower  parts  of  the  same 
meridian,  it  is  about  70°.  The  intermediate  merid- 
ian will  be  found  to  have  intermediate  perception 
from  the  two  nearest  principal  meridians.  The 
perception  of  the  left  eye  is  practically  the  same. 
The  normal  extent  of  the  visual  field  is  largely  in- 
fluenced by  the  parts  surrounding  the  eye,  such  as 
the  bony  prominences,  nose,  moustache,  etc.,  so  it 
is  necessary  when  you  wish  to  depend  upon  your 
findings,  to  associate  it  with  other  examinations, 
such  as  an  ophthalmoscopic  examination  of  the 
fundus,  and  a  test  to  determine  the  central  visual 
acuity. 

Q.  How  many  methods  are  there  for  deter- 
mining the  visual  perception? 


152    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 
Figure  23. 


Dr.  Skeel's  Self-Recoeding  Perimeter. 

"The  instrument  here  shown  is  the  result  of  experiments  ex- 
tending over  some  years,  in  the  endeavor  to  construct  a  Perimeter 
which  would  be  self-recording,  and  at  the  same  time  simple  in  its 
construction.  In  the  use  of  the  ordinary  instrument,  the  examiner's 
attention  is  divided  between  watching  the  eye  of  the  patient,  the 
position  of  his  own  hand  carrying  the  test  object,  in  reading  the 
graduations  on  two  arcs,  and  in  marking  down  the  same  on  the 
chart. 

In  the  instrument  here  described,  the  reading  of  the  gradua- 
tions is  entirely  dispensed  with,  and  the  recording  of  the  position  of 
the  test  object  simplified  to  the  pressing  of  a  lever.  The  appear- 
ance of  the  instrument  is  plainly  shown  in  the  cut," 


PERIMETRY.  153 

A.  There  are  several,  siieli  as  the  bhxckboard 
test,  the  finger  test,  but  the  principal  one  and  the 
one  now  most  extensively  used,  is  the  test  by 
means  of  an  instrument  called  the  perimeter. 
Tliere  are,  like  all  other  instruments,  a  number  of 
dilferent  kinds  of  perimeters  to  be  found  on  the 
market;  but  an  automatic,  self -registering  perime- 
iev,  made  by  JMeyrowitz  Bros,  of  New  York  city,  I 
believe  to  be  the  most  perfect  instrument  of  its 
kind.  They  are  all,  however,  based  on  the  same 
principle  of  having  an  object  of  definite  size  and 
color  to  a])pear  to  every  point  of  the  retina.  This 
can  only  be  accomplished,  and  is,  by  moving  the 
object  in  different  meridians  along  the  inner  sur- 
face of  an  arc,  sufficiently  long  to  describe  a  quar- 
ter of  a  circle  at  least.  This  arc  is  black  on  its  sur- 
face, and  is  divided  into  degrees  from  0^  to  90^,  on 
each  arm,  and  when  rotated,  it  describes  the  figure 
of  a  hoUow  sphere. 

Charts  on  which  to  record  the  result  of  peri- 
metric observations  accompany  the  instruments, 
and  are  necessar}^  to  preserve  a  record  of  your 
cases. 

In  using  the  perimeter,  your  patient  is  seated 
with  his  back  to  a  good  light,  and  the  chin  resting 
on  the  chin-rest  of  the  perimeter.  The  eye  to  be 
examined  is  directed  to  a  fixation  point  in  the  cen- 

Vi 


154    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

ter  of  the  arc  of  the  perimeter.  The  other  e^^e  is 
eoA^ered  by  the  hand  or  handkerchief  of  the  pati- 
ent. The  test  object  is  generally  a  white  square, 
five  millimetres  each  way,  and  is  moved  along  the 
perimeter  from  the  periijhery  towards  the  central 
fixation  point.  The  movement  of  the  object  must 
not  be  too  rapid,  and  as  soon  as  it  comes  within 
the  field  of  vision  and  can  be  readily  recognized  by 

Figure  23. 


^y 


\ 


tMERSON'S  fERIMETER  CHAH  r 
MEYPOWITZ  DROS.N.Y. 


its  color,  you  cease  the  moving  and  note  the  point 
as  marked  on  the  perimeter  in  degrees.  This  will 
indicate  the  visual  perception  for  this  meridian, 
and  you  proceed  to  examine  the  various  other  me- 
ridians in  the  sajne  manner,  generally  selecting 
the  principal  meridians  first.  After  reaching  the 
point  where  the  object  first  becomes  visible,  and 


PERIMETRY.  155 

after  making  a  note  of  it  on  your  chart,  you  pro- 
ceed to  examine  for  blind  spots,  or  scotoma,  as 
they  are  called.  These  are  spots  on  the  retina  that 
have  lost  their  perception,  either  totally  or  par- 
tially, from  disease  or  other  causes.  They  are  re- 
cognized by  the  object  becoming  invisible  as  it  is 
moved  along  the  arc  of  the  perimeter  at  certain 
points. 

If  there  are  no  scotoma  present  in  the  exam- 
ined eye,  the  test  object  will  remain  in  view  from 
the  moment  when  it  is  first  observed  until  it 
reaches  the  central  point  of  the  arc.  There  is  one 
point,  however,  which  will  be  found  on  the  tem- 
poral side  in  the  horizontal  meridian,  and  at  a 
point  on  the  perimeter  marked  10°,  where  the  test 
object  will  be  invisible  for  a  perceptible  space. 
This  is  called  the  blind  spot  of  the  eye,  which  is  a 
normal  condition  and  corresponds  to  the  optic 
nerve  disk,  this  part  of  the  eye  being  devoid  of  vis- 
ual perception.  This  spot  is  also  called  the  blind 
spot  of  Mariotte,  and  must  not  be  confounded  with 
other  blind  spots,  or  scotoma,  that  may  be  found 
during  a  perimetric  examination,  and  are  the  re- 
sult of  pathological  change.  You  must  not  forget 
that  when  you  are  examining  the  temporal  merid- 
ian, it  is  the  nasal  side  of  the  eye  you  are  testing, 
and  Avhen  examining  the  upjjer  part  of  the  verti- 
cal meridian,  it  is  the  lower  part  of  the  retina  that 


156    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

is  under  observation.  In  other  words,  tliat  it  is  al- 
waj'S  the  opposite  side  of  the  retina  that  is  beinj>' 
examined  when  measuring  tlie  visual  field  in  any 
particular  meridian. 

Q.  Is  a  generally  contracted  field  necessarily 
significant? 

A.  Yes,  it  is  very  significant,  as  it  will  be 
many  times  the  first  intimation  we  may  receive  as 
to  very  serious  pathological  changes,  which  may 
prove  very  inimical  to  sight,  if  it  does  not  in  time 
result  in  total  blindness;  hence  its  importance 
from  a  clinical  and  diagnostic  standpoint.  Con- 
tracted fields  of  vision  are  to  be  found  in  such  j)a- 
thological  conditions  as  glaucoma,  or  hardening 
of  the  eye-ball;  papillitis,  or  choked  disk;  retinitis, 
choroiditis,  and  choroido-retinitis,  and  many  oth- 
er of  the  diseased  conditions  of  the  eye.  For  this 
reason,  we  have  felt  justified  in  saying  a  few  words 
in  regard  to  the  perimeti'ic  examinations  of  the 
eye. 


CHAPTER  XIII. 


Illustrative  Cases  From   Note  Book. 

In  this  chapter  we  shall  endeavor  to  bring  to- 
gether a  number  of  cases  of  the  different  forms  of 
refractive  error  that  have  been  considered  in  the 
preceding  chapters,  for  the  purpose  of  placing  in  a 
comi^act  and  convenient  form,  the  different  refrac- 
tive condition  recognized  at  the  present  time. 

In  doing  this,  we  shall  make  a  selection  of 
cases  from  our  case  book,  with  a  single  object  in 
view,  and  that  is,  to  select  such  as  will  clearly  and 
emphatically  demonstrate  the  particular  case  un- 
der consideration. 

Several  cases  of  each  variety  of  refractive 
error  will  be  cited,  beginning  with  the  most  fre- 
quent of  them  all,  that  is,  simple  hypermetropia,or 
hyperopia,  as  it  is  sometimes  called. 

Simple  Hypermetropia. 

Case  I.    Mrs.  W.  H.,  age  73  years: 

KE.V.  =  T^<Vw.  -I-3D.S.  =  ff 
L.  E.  V.  =  ^^w.  -1,-3  D.  S.  =  f|. 

157 


158    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Ordered  the  above  for  distance,  to  be 
worn  all  the  time. 

Case  II.    Mr.  T.,  age  55  years: 

E.  E.  V.  =  f^  w.  -[-  4.50  D.  S.  =  ||. 
L.  E.  V.  =  ^  w.  -I-  4.50  D.  S.  =  H. 

Ordered  the  above  for  constant  wear, 
with  separate  correction  for  his  presby- 
opia. 

Case  III.    Miss  S.,  at»e  15  years: 


K. 

E. 

V. 

20 

50 

w. 

-I-2.25D.  S. 

20 

2  0- 

L. 

E. 

V. 

20 

40 

w. 

-1-  2.50  D.S. 

. 20 

—  2ir- 

Ordered  the  above  for  constant  wear, 

IMiss  L 

.,  age 

IS 

years : 

E. 

E. 

V. 

20 

40 

w. 

-1  -  75  D.  S.  = 

_    20 
~    21)' 

L. 

E. 

V. 

20 

w. 

-1-75  D.  S.  = 

_    20 
-    2-0- 

The  ophthalmoscope  and  retinoscope 
showed  hypermetropia  of  4  D.  S. 

Ordered    solution    of    atropine    for 
three  days,  with  the  following  results: 

B.  E.  V.  =  A<V  w.  -I  -  3.25  D.  S.  =  H- 
L.  E.  V.  =  A\  w.  -I  -  3.25  D.  S.  =  H. 


Ordered  a  -f-  2  D.   S.   for   constant 
wear  with  good  result  and  relief  of  all  as- 


ILLUSTRATIVE  CASES.  159 

thenopia,    thoiigli    she    had    previously 
complained  a  great  deal  of  her  eyes. 

This  shows  us  two  varieties  of  hyper- 
metropia.  The  0.75  D.  S.  represents  the 
manifest  hypermetropia,  while  the  differ- 
ence in  this  lens  and  the  3.25  D.  S.  repre- 
sents the  latent  hypermetropia,  that  is 
2.50  D.  S.  The  fact  that  she  did  not  ac- 
cept the  4  D.  S.,  as  shown  by  the  ophthal- 
moscope, was  probably  due  to  some  little 
spasm  of  the  accommodation,  even  after 
using  atropine  three  days,  as  this  is  not 
always  long  enough  to  continue  it  to  per- 
fectly relax  the  ciliary  muscles;  but  it  is 
not  always  practical  to  continue  it  for  a 
longer  period,  owing  to  the  resulting  in- 
convenience. 

Case  V.    Chas.  S.,  age  17  years. 

Internal  strabismus,  or  squint.  Both 
eyes  corrected  by  operation . 

R.  E.  V.  =  fA  w.  -I,-  .75  D.  S.  =  U- 
L.  E.  Y.  =  2I0  w.   2.25  D.  S.  =  tVt- 

This  is  an  interesting  case,  as  it  re- 
presents three  separate  conditions.  First, 
there  is  squint,  or  strabismus;  second, 
there  is  a  condition    of    anisometropia; 


160    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

tliii'd,  tlK'io  is  a  (•(niditiou  of  amblyopia 
ex-anoi>sia  in  tlu*  left  eye,  a  eoiiditioii,  tis 
we  have  seen,  that  is  veiT  often  found  in 
these  cases. 

After  "getting-  the  eyes  straightened 
np  in  good  shape  by  a  tenotomy  on  botli 
internal  recti,  and  giving  liim  tlie  above 
correction  for  constant  wear,  I  could  see 
no  improveinent  in  the  perceptive  power 
of  the  left  eye,  thougli  lie  was  under  my 
observation  for  five  years. 

Tlu're  is,  no  doubt,  a  condition  of 
nou-de\elo]tment  of  the  perceptive  ele- 
ments of  this  eye,  and  hence  no  prospect 
of  its  imi)roving  to  any  great  extent. 

In  the  next  class  of  cases  we  shall  call 
your  attention  to  Simple  HyiJermetropic 
Astigmatism. 

Case  1.    ]M i ss  C.  II.,  age  28  years.    Teacher : 

K  E.  V.  =  T^^  w.  -i-  3.50  D.  cyl.  cax.   90"  = 

20       I 
T(J  'I"- 

L.  E.  V.  =  t'j/'o  w.  -I  -  3.50  D.  cyl.  ax.   90°  = 

20 
30- 

This  correction  was  ordered,  in  a  well 
littiug     spectacle    frame,  with  the  most 


ILLUSTRATED  CASES.  161 

happy  results.  Before  I  saw  her  she  was 
wearing-  a  -|-  2  D.  cyl.  ax.  90°,  both  eyes, 
with  I"  vision.  This  was  the  best  she  had 
ever  seen. 

This  beiiig  hypermetropic  astigma- 
tism, with  axis  at  90°,  it  is  "according  to 
the  rule." 

The  next  case  is  one  "contrary  to  the 
rule". 

('ase  II.    J.  M.,  age  37  years.    Farmer: 

R.  E.  V.  =  U  w.  -1-0.75  D.  cyl.  ax.  180°  =- 

20      I 

2  0  "r  • 
L.  E.  Y.  =  14  w.  -1-1.25  D.  cyl.  ax.  180°  = 

2  0* 

Ordered  for  constant  wear,  and  as  he 
is  not  jet  presbyopic,  he  can  use  them  for 
all  kinds  of  work. 

Cnse  III.     "Between  the  rules." 

JMiss  H.  H.,  age  36  years : 

E.  E.  V.  =  f«-w.   -1-    1-  D.   cyl.    ax.    15«   = 

2,0      I 
2  0    "I  "• 

L.  E.  V.  =  14  w.  -|-  .67  D.  cyl.    ax.    165°  = 

20 
20" 

In  this  case,  you  will  observe  the  axis 
of  the  astigmatism  to  be  neither  "with'^ 
or  "against  the  rule,"  but  at  an  intermed- 
iate point.    You  will  observe,   however, 


162    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

that  the  axis  in  each  eye  points  in  the 
same  direction,  towards  the  nose.  This 
is  usually  the  case  to  which,  however, 
there  are  many  exceptions. 

The  next  variety  of  hypermetropia 
to  engage  our  attention  is  hypermetropia 
complicated  with  astigmatism,  or  Com- 
pound Hypermetropic  Astigmatism. 

Case  I.    "With  the  rule." 
Mrs.  H. : 

R.  E.  Y.  =  20  ^,  .|.  1.75  D.  S.   C  -I-   1  D. 

cyl.  ax.  yOo  =  14. 
L.  E.  V.  =  11  w.  -1-  1.75  D.  S.  C  -I-   1   D. 

cyl.  ax.  90°  =  f|. 

Case  IT.    "Against  the  rule.'' 

Miss  J.  C,  age  15  years: 
K  E.  V.  =  ^%  w.  -\r  2.75  D.  S.  C  -|-   2.25 


D.  cyl.  ax.  180«  =  f 


L.  E.  V.  =  2V0  w.  -I-  2.75  D.  S.  C  -|-   2.25 
D.  cyl.  ax.  180«  =  U. 

Case  III.    Between  the  rules. , 

Mr.  S.,  age  57  years: 

K  E.  V.  =  ^\  w.  -1-  1-25  D.  S.   C  -1-  1-50 
D.  cyl.  ax.  95°  =  |^. 

L.  E.  V.  =  2^w.  -1-  2.50  D.S.   C  -|-  1-50 
D.  cyl.  ax.  85°=  ^ -\-. 


ILLUSTRATED  CASES.  163 

Case  TV.    The  same. 

Mrs.  I.  C,  age  47  years: 

R.  E.  V.  =  f«-  w.  -I-  1.50  D.  S.  3-1-  .55  D. 

cyl.  ax.  135°  =  ||. 
L.  E.  V.  =  1^  w.  -I-  1.50  D.  S.  r:  -I-  .55  D. 


To 

^o  

2  0 


cyl.  ax.  30°  —  ^Ji 


In  this  ease  you  will  observe  that  the 
axes  of  the  cylinder  both  point  towards 
the  temple. 

The  next  class  of  refractive  errors  to 
illustrate  are  the  myopic  varieties,  and 
we  will  begin  with  Simple  Myopia. 

Case  I.    ]\rrs.  J.  S.,  age  30  years: 

K  E.  V.  =  20  w.  —  3  D.  S.  =  U  -I-. 
L.  E.  V.  =  1^  w.  —  3  D.  S.  =  M  -I-- 

Ordered  the  above  glass  for  constant 
wear. 

Case  II.    H.  G.,  age  51  years. 

Anisometropia: 

R.  E.  V.  =  ^\  w.  —  5.50  D.  S.  =  |^. 
L.  E.  V.  =  2V0  w.  —  6.50  D.  S.  =  f^. 

Ordered  the  above  glasses  for  both 
distant  and  close  work,  with  satisfactory 

results. 


164    REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

In  cases  where  there  is  not  more 
than  one  or  two  dioptres  difference  in  the 
eyes,  you  can  generally  correct  both  eyes 
separately,  though  you  are  not  always 
able  to  do  so.  Each  case  must  be  a  rule 
unto  itself. 

Myopic  Astigmatism  "with  the  rule." 
Case  I.    Miss  S.,  age  31  years: 

E.  E.  V.  =  U  w.  —  2.50  D.  cyl.  ax.  ISO^  = 

20 
30* 

L.  E.  V.  =  U  w.  —  2.50  D.  cyl.  ax.  l&O^  = 

2_0 
"3  0"' 

This  is  the  best  I  could  do  in  this 
case,  but  this  being  the  first  time  she  ever 
had  her  refractive  error  corrected,  may 
account  for  it  to  a  certain  extent.  I  have 
not  been  able  to  note  whether  any  im- 
provement has  occurred  or  not,  but  like- 
ly there  has  been  some  increase  in  the 
visual  acuteness. 

Case  II.    ''Against  the  rule," 

F.  Van  W.,  age  22  years: 
K.  E.  V.  =  |«  w.  —  .55     D.  cyl.   ax.  90°  = 

20         I      • 


L.  E.  V.  =  |«   w.  —  .55   D.  cyl.    ax.  90° 

2  0       I 
2  0     "I  " 

For  constant  wear. 


ILLUSTRATED  CASES.  165 

Case  111.    "Between  the  rules." 

Miss  A.  E.,  age  28  years: 
E.  E.  V.  =  fl  w.    —   1   D.   cyl.  ax.  105°  = 


20 
2  0- 


L.  E.  V.  =  U  w.  —  1.50  D.  cyl.  ax.  60° 


20 
20' 


You  will  notice  that  there  is  a  little 
difference  in  the  axes  of  the  two  eyes. 

The  next  class  of  cases  is  myopia, 
C()m])licated  with  astigmatism. 

(Ijise  1.    INIrs.  D.,  age  29  years: 

E.  E.  V.  =^  ^V  w.  —  1  D.  S.  C  —   2.75   D. 

cyl.  ax.  180°  =  ||. 
L.  E.  V.  =  ^^%  w.  —  1  D.  S.  C  —  2.75   D. 

cyl.  ax.  180O  =  f^. 

In  the  above  formula  you  will  ob- 
serye  the  astigmatism  is  "according  to 
the  rule." 

Case  II.    "Against  the  rule." 

Miss  T.,    age  23  years: 

E.  E.  V.  —  ^V^  w.  —  1.25  D.   S.  C  —  2.25 

D.  cyl.  ax.  90°  =  |^. 
L.  E.  V.  =  2  0(7  w.  —  1.25  D.   S.  C   —  1.25 

D.  cyl.  ax.  90°  =  ff . 

u 


166    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

You  will  observe  we  are  not  able  in 
this  case  to  bring  the  vision  up  to  |^,  or 
normal,  a  result,  as  we  observed  by  the 
ophthalmoscope,  of  pathological  change 
in  the  fundus  of  the  eye,  as  we  are  apt  to 
have  in  high  degrees  of  ametropia,  of  the 
myopic  variety. 

Case  III.    "Between  the  rule." 

,  L.  N.,  age  16  years: 

E.  E.  V.  =  |o  w.  —  .75  D.  S.   C  —  -55  cyl. 

ax.  120°  =  f|. 
L.  E.  Y.       H  w.  —  .75  D.  S.  C  —   .27  cyl. 

The  last  variety  of  refractive  errors 
to  which  we  wish  to  call  your  attention  is 
Mixed  Astigmatism. 

Case  I.    Mr.  P.,  age  36  years: 

E.  E.  Y.  =  1^  w.  —  1  D.  cyl.  ax.  180°  C 
-I-  67  D.  cyl.  ax.  90°  =  H. 

L.  E.  Y.  =  H  w.  —  1  D.  cyl.  ax.  180«  C 
-I  -  75  D.  cyl.  ax.  90°  =  |^. 

You  will  observe  that  the  above  for- 
mula calls  for  a  cross  cylinder,  so  for  rea- 
sons already  given,  I  prescribed  the  fol- 
lowing: 

E.  —  1  D.  S.  C  -I-  1.67  D.  cyl.  ax.  90°. 
L.  —  1  D.  S.  C  -1-  1.50  D.  cyl.  ax.  90«. 


ILLUSTRATED  CASES.  167 

Case  II.    J.  p.,  age  45  years: 

E.  E.  V.  ==  f^  w.  —  .55  D.  cyl.  ax.    180«  C 


75  D.  cyl.  ax.  90°  = 


L.  E.  V.  =  H  w.  —  .55  D.  cyl.  ax.   180°  C 
-1  -  67  D.  cyl.  ax.  90°  =  |^. 

I  prescribed  the  following  formula: 
R.  —  .55  D.  S.  C  -I-  1-25  D.  cyl.  ax.  90«. 
L.  —  .55  D.  S.  C  -I-  111  I>.  cyl.  ax.  90°. 

This  man  was  exceedingly  nervous, 
and  at  the  present  time,  four  years  after 
fitting  his  eyes,  he  tells  me  he  has  been 
very  much  better  since  he  has  been  wear- 
ing glasses. 

In  testing  this  class  of  cases,  you  can 
use  the  cylinders  as  above,  or  you  can 
test  them  by  using  the  sphericals  and  cy- 
linders combined,  as  in  the  prescription. 
The  result  in  either  case  you  will  find  to 
be  the  same. 

With  this  we  shall  pass  to  the  consid- 
eration of  specimen  cases  complicated 
with  presbyopia,  and  we  shall  adhere  to 
the  same  plan  we  adopted  in  the  begin- 
ning, of  taking  up  each  separate  form  of 
refractive  error,  and  consider  it  in  con- 
nection with  this  condition: 

Simple  Hypermetropia,  complicated 
with  presbyopia. 


168    REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

Case  I.    Mrs.  McD.,  age  54  years: 

R.  E.  V.  =ft  w.  -I-  1.T5  D.  S.  =  |«. 
L.  E.  V.  =  U  w.  -I-  1-75  D.  S.  =  II 

In  tliis  case  tlie  near  point,  even  with 
the  above  correction,  was  so  far  off  that 
she  could  not  use  her  eyes  for  close  work. 
In  order  to  bring  back  the  near  point  to 
where  she  coukl  read  No.  1  Jagar  at  IG 
inches,  it  was  necessary  to  add  a  2.00  D., 
which  you  see  agrees  pretty  closely  to  the 
general  rule  in  these  cases,  so  with  a  2.00 
D.  S.  —  to  1.75  D.  S.  =  3.75  D.  S.  for  close 
work  or  reading,  so  it  was  necessary  to 
prescribe  two  pairs  of  glasses,  one  for  dis- 
tance, a  — -1.75  D.S.,  and  one  for  close 
work,  a  -|-3.75  D.S.  These  could  be  put  in 
separate  frames,  or  they  could  be  put  up 
in  a  bifocal  lens,  which  for  many  people 
is  a  very  convenient  form,  as  it  obviates 
the  necessity  of  carrying  about  two  pairs 
of  glasses,  as  well  as  the  constant  chang- 
ing; or  the  distance  may  be  worn  in  a 
spectacle  frame,  and  a  grab  frame  con- 
taining the  presbyopic  correction  placed 
in  front  of  these  for  close  work.  This  also 
I  find  a  convenient  method  in  many 
cases,  the  great  objection  to  them  being 
the  additional  weight  and  the  air   space 


ILLUSTRATED  CASES.  169 

between  the  pairs  of  lenses,  though  I  find 
many  who  prefer  it  to  the  bifocal  lens,  as 
many  complain  of  the  disagreeable  neces- 
sity of  having  to  look  through  the  strong- 
er leuvses  wlien  walking.  Many  also  com- 
plain of  the  straight  or  curved  line  to  be 
always  found  in  the  bifocal  lens.  How- 
ever, the  manner  of  wearing  double  cor- 
rections is  largely  a  personal  matter,  and 
each  case  must  be  decided  on  its  individ- 
ual merits. 

Case    II.     Simple    Hypermetropic    Astigmatism, 
complicated  with  presbyopia. 

Miss  T.,  age  60  years: 

E.  E.  V.  =  tl  w.  -I-  2.25  D.  cyl.  ax.    90«  =- 

20 
2  U« 

L.  E.  y.  =  f^  w.  -1-2.25  D.  cyl.  ax.    90°  = 

2  0 
20* 

This  correction  rendered  her  eyes 
emmetropic,  and  at  60  years  of  age  the 
presbyopia  generally  requires  a  3  D.,  so 
with  a  -r-  3  D.  added,  she  can  read  No.  1 
Jager  at  about  16  inches,  a  point  I  deem 
sufficiently  close  for  ordinary  working- 
purposes.  This  lady  preferred  the  two 
pairs  in  separate  frames,  so  I  prescribed 
the  above  formula  for  distance,  and  the 


170    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

same  with  a  ^-  3  D.  S.  added  for  her  pres- 
byopia as  follows: 

-I-  3  D.  S.  C  w.   -1-2.25  D.  cyl.  ax.  90°   for 
both  eyes. 

Case  III.  Hypermetropia  and  Astigmatism,  or 
Compound  Hypermetropic  Astigmatism, 
complicated  with  presbyopia. 

Miss  C,  age  63  years : 


TffTT 


I-  1.25  D.  S.  C  -1-  111 
D.  cyl.  ax,  15°  =  ||. 
L.  E.  V.  =  ^  w.  -I-  1.25  D.   S.  C  -I-   ID 
cyl.  ax.  165°  =  ||. 

The  above  correction  rendered  her 
eye  practically  emmetropic,  so  all  we 
have  to  do  is  to  calculate  what  glass  she 
will  need  to  correct  her  presbyopia,  and 
at  63  years,  we  would  expect  that  she 
would  require  something  more  than  3  D., 
so  by  testing  for  No.  1  Jager  at  16  inches, 
we  find  it  requires  a  -^  3.25  D.  over  the 
above  correction  for  distance;  so  we  must 
add  this  on  to  the  above  spherical  to  get 
her  reading  glasses,  and  we  find  that  3.25 
D.S.  —1.25  D.S.  =  4.50  D.S.,  so  we  must 
have  for  her  reading  formula  the  follow- 
ing: 


ILLUSTRATED  CASES.  171 

E.  -I-  4.50  D.  S.  C  -I-  l.ll'D.  cyl.  ax.  15«. 
L. -I-4.50D.  S.  C-l-l.OOD.  cvl.   ax.   165«. 


while  for  her  distant  correction,  we  pre- 
scribed the  combination  we  found  neces- 
sary to  restore  her  eyes  to  a  condition  of 
emmetropia,  as  given  above. 

Case  IV.    Simple  Myopia,  with  presbyopia. 
Mr.  S. :  age  51  years. 


E.  E.  V.  =  II  w.  —  1.00  D.  S.  =  fl 


L.  E.  V.  =  Uw.  —  1.00  D.  S. 


2.0 
20 


This  man  being  myopic  1  D.,  it  will 
put  off  his  presbyopia  at  least  five  years, 
and  as  evidence  we  do  not  find  him  seek- 
ing aid  for  his  eyes  for  close  work  until  51 
years  old,  instead  of  at  43  or  45,  as  is  the 
case  with  an  emmetrope;  ordinarily,  at 
50  an  emmetrope  will  require  about  2  D. 
for  presbyopia,  but  as  the  myopia  com- 
pensates for  1  D.,  we  find  all  he  will  re- 
quire to  correct  his  presbyopia  is  a  convex 
lens  of  1  D.,  which  we  prescribe  with  sat- 
isfaction. 


172    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Case  V.     Simple  Myopic  Astigmatism,  complicat- 
ed with  presbyopia, 

''a."     '^With    the   rule." 

Mrs.  M.  S.,  age  49  years: 
E.  E.  V.  =  fo  w.  —  1.25  D.  cyl.  ax.  180°   = 

2  0 

L.  E.  V.  =  fo-  w.  —  1.25  D.  cyl.  ax.  180°  = 


2  0 
2  0 


You  will  see  that  this  lady  is  emme- 
tropic in  one  meridian  and  myopic  in  the 
other.  She  will  begin  to  be  presbyopic  in 
the  emmetropic  meridian  shortly  after 
forty,  and  at  fifty  will  need  2  D.  to  correct 
the  presbyopia  in  this  meridian;  but  in 
the  myopic  meridian  she  will  not  begin 
to  get  presbyopic  for  at  least  five  years 
later,  so  it  will  never  do  to  give  her  the 
same  correction  in  both  meridians,  so  we 
must  give  her  1  D.  to  corn  ct  her  myopic 
meridian  and  2  D.  to  correct  her  emme- 
tropic meridian.  This  can  only  be  done 
by  combining  sj^herical  and  cylindrical 
lenses  together,  and  a  little  reflection 
will  show  what  combination  you  will 
need  for  reading  glasses,  which  is  as  fol- 
lows: 


ILLUSTRATED  CASES.  173 

K.  -1-  1  D-  S.  C  -I-  1  r>.  cyl.  ax.  90°. 
L.  -I  -  1  D.  S.  C  -I  -  1  D.  cyl.  as.  90°. 

"b."    "Against  the  rule.'' 

Mr.  C,  age  55  years: 

R.  20  ^.  _  2  D.  cyl.  ax.  90«  =  U- 
L.  20  ^,  __  2  D.  cyl.  ax.  90°  =  |^. 

This  man  is  only  presbyopic  in  the 
vertical  meridian,  as  two  dioptres  of  my- 
opia Avill  postpone  his  presbyopia  for  ten 
years,  but  we  find  him  slightly  presbyopic 
in  this  meridian,  as  he  is  55  years  old,  so 
we  find  that  we  shall  have  to  correct  each 
meridian  separately,  as  in  a  former  case. 
Xow  in  the  vertical  meridian  he  will  re- 
quire two  and  a  half  dioptres,  while  in 
the  horizontal  we  find  he  will  not  require 
more  than  half  a  dioptre.  By  testing  each 
eye  with  No.  1  Jager,  we  find  that  this  is 
just  what  he  does  require  for  his  close 
work,  so  we  prescribe  the  following  for- 
mula for  both  eyes: 
-I-  .55  D.  S.  C  -I-  '-^  D-  cyl.  ax.  180°. 
and  we  find  that  our  patient,  who,  by  the 
way,  is  a  busy  merchant,  and  uses  his 
eyes  a  great  deal  at  his  books,  has  little  or 
no  trouble  with  his  eyes.  I  insisted  on  his 
wearing  his  distant  correction    all    the 

15 


174    REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

time  when  not  usinii"  his  eyes  for  close 
work. 

Case  YI.    "c."    "Between  the  rule." 

J.  E.,  age  45  years: 


E.  II  w.  —  .55  D.  cyl.  ax.  135o  =  f|. 


w.  —  .67  D.  cyl.  ax.  45o  =  |o. 


This  man  is  only  presbyopic  in  his 
emmetropic  meridian,  so  he  will  require 
a  cylindrical  correction  alone;  and  as  the 
presbyopia  is  always  at  right  angles  to 
the  myopic  astigmatism,  we  find  that  he 
accepts  with  perfect  correction  of  his 
slightly  advanced  presbyopia,  the  follow- 
ing: 

R.  -I-  75  D.  cyl.  ax.  45°. 
L.  -I-  75  D.  cyl.  ax.  135°. 

Correcting  the  presbyopia  in  the 
more  advanced  cases  of  myopia,  will  only 
require  a  reduction  in  the  strength  of  the 
concave  spherical  lens  necessary  to  cor- 
rect their  distant  vision.  For  further  in- 
formation on  this  point,  I  refer  you  to  the 
chapter  on  myopia  and  its  correction. 


ILLUSTRATED  CASES.  175 

Muscular  Deficiencies  : 

Case  I.  Miss  E.  31.,  age  22  years,  saleslady,  com- 
plained of  asthenopia  and  headache,  be- 
sides various  other  nervous  manifesta- 
tions. 

R.  E.  V.  f^  -|-  no  improvement  with  glasses. 
L.  E.  Y.  f^  -|-  no  improvement  with  glasses. 

Ophthalmoscope      showed     normal, 
healthy  fundus,  refraction  emmetropic. 

Muscle  tests  showed   the  following: 

Adduction,  8°. 
Abduction,  lO^. 
Exophoria,  4°. 

I  advised  a  tenotomy  of  the  external 
recti,  but  it  was  refused.  I  then  pre- 
scribed a  prismatic  lens  1|°,  base  in,  over 
■  both  eyes,  to  be  worn  -all  the  time.  That 
is  nearly  three  years  since,  and  though  I 
have  often  met  her,  she  has  never  com- 
plained of  her  eyes,  more  than  to  say  that 
she  could  not  go  without  her  glasses  for 
any  length  of  time  without  a  return  of  the 
eye-strain.  It  is  always  best,  when  prac- 
tical, to  prej>cribe  prisrn  in  a  well  adjust- 
ed, comfortably  fitting  riding  boAv  spec- 
tacle frame. 


176    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Case  II.  Mrs.  S.,  age  31  years,  complained  of  pain 
in  her  eyes  and  blurring,  as  well  as  severe 
headache  and  many  other  nervous  symp- 
toms. 

R.  E.  V.  1^.      No  improvement  with  glasses. 
L.  E.  y.  |-^.      No  improvement  with  glasses. 

Muscle  test  showed: 

Adduction,  14°. 
Abduction,  9°. 
Circumduction,  3°. 
Exophoria,  5°. 

Advised  tenotomy  of  external  recti, 
but  refused.  Prescribed  2°  prism,  base 
in,  to  be  worn  all  the  time,  with  almost 
complete  I'elief  of  the  asthenopia  while 
wearing  the  glasses.  I  met  this  lady  some 
time  afterwards,  Avhen  she  said  she  was 
under  eternal  obligation  to  me  for  having 
so  readily  relieved  her  of  her  horrible 
headache,  from  which  she  had  suffered 
so  long  and  had  spent  so  much  money 
trying  to  get  rid  of,  by  doctoring  and  tak- 
ing all  sorts  of  headache  medicines  with- 
out effect. 


ILLUSTRATED  CASES.  177 

Case  III.    Hyper-exophoria. 

Mrs.  M.,  age  46  years. 

R.  E.  V.  1^.     No  improvement  with  glasses. 
L.  E.  Y.  f^.     No  improvement  with  glasses. 

This  woman  was  referred  to  me  by 
her  brother,  a  physician  in  good  standing 
and  large  practice.  She  was  an  exceed- 
ingly nervous  lady,  a  confirmed  neiires- 
thenic,  w^as  prematurely  gray  and  aged, 
had  had  severe  headaches  for  years  back, 
had  undergone  an  operation  for  uterine, 
or  ovarian  trouble,  in  hopes  of  getting  re- 
lief, without  avail. 

Muscle  test  showed  the  following 
condition: 

Adduction,  8°. 
Abduction,  14°. 
Exophoria,  5°. 
Hyperphoria,  2°. 

Advised  an  operation,  which  she  ac- 
cepted. Cut  both  external  recti  within  a 
few  days  of  each  other,  as  she  lived  some 
distance  and  was  anxious  to  get  home. 
Have  only  heard  from  her  once,  when  she 
reported  herself  very  much  better  in  ev- 
ery possible  way. 


178    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Case  III.    Mrs.  P.,  age  30  years,  complained  of  eye- 
strain. 

B.  E.  V.  1^.      No  improvement  with  glasses. 
L,  E.  V.  f^.      No  improvement  with  glasses. 

Ophthalmoscope  showed  normal 
fundus  and  emmetropic  refraction. 

Muscle  test  showed: 

Adduction,  24°. 
Adbuction,  0°. 
Circumduction,  3°. 

This  woman  showed  an  esophoria  of 
2°,  notwithstanding  the  muscle  power  ap- 
peared pretty  well  distributed.  I  pre- 
scribed a  -JO  prism,  base  out,  with  consid- 
erable benefit;  and,  as  she  says,  with  a  re- 
lief of  all  her  asthenopia. 

Case  IV.    Mrs.  K.,  age  26  years,  complained  a  great 
deal  of  her  eyes  and  headache. 

R.  E.  V.  ff .      No  improvement  with  glasses. 
L.  E.  V.  ff .      No  improvement  with  glasses. 

Ophthalmoscope  showed  a  healthy 
and  emmetropic  eye. 


ILLUSTRATED  CASES.  179 

Muscle  test  showed: 

Adduction,  20°. 
Abduction,  4°. 
Esophoria,  3°. 

Prescribed  a  1°  prism,  base  out,  with 
marked  improvement. 

I  think  we  have  given  a  sufficient  number  of 
examples  of  the  different  refractive  errors  and  the 
different  muscular  insufficiencies,  to  serve  our  pur- 
pose of  showing  how  these  cases  run  in  practice,  as 
well  as  the  methods  adopted  in  correcting  them. 
These  sami)le  cases  have  been  selected  from  our 

case  book,  with  only  one  object  in  view,  and  that 
to  illustrate  the  particular  form  of  difficulty  under 
consideration.  Of  course,  we  might  continue  this 
ad  infinitum,  but  we  do  not  deem  it  necessary. 

Now,  in  regard  to  prescribing  what  particular 
kind  of  frame  each  case  should  wear,  there  is  one 
thing  you  should  always  insist  on,  and  that  is,  for 
cylindrical  and  prismatic  lens  always  try  to  have 
them  wear  a  well-fitted  and  perfectly  centered 
spectacle  frame.  If  they  will  not  do  this,  as  is  of- 
ten the  case,  then  the  only  alternative  is  the  offset 
nose  glass,  which  will  many  times  do  as  well. 

In  the  cases  of  latent  hypermetropia  that  re- 
quire the  use  of  a  mydriatic,  (which  are  drugs  that 
dilate  the  pupil  and  paralyze  temporarily  the  ac- 


180    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

tion  of  the  ciliary  muscle,  thus  counteracting  any 
spasm  of  the  accommodation,)  the  most  frequently 
used  is  a  solution  of  atropine  sulphate,  4  grains  to 
the  ounce  of  distilled  water,  1  or  2  droiDS,  instilled 
into  the  eye  every  four  hours  for  three  days,  gener- 
ally suffice.  It  takes  at  least  twelve  days,  and  of- 
ten longer,  to  recover  from  the  use  of  this  drug, 
hence  it  is  very  objectionable  for  this  purpose, 
H^'oscyamine  is  used  for  this  purpose,  also,  in  the 
strength  of  two  grains  to  the  ounce  of  water.  The 
effect  lasts  from  seven  to  ten  days.  Perhaps  the 
best  drug  for  this  purpose,  but  the  most  expensive, 
is  a  solution  of  eight  grains  to  the  ounce  of  water> 
of  homatropine.  One  drop  of  this  solution  in  each 
eye  every  fifteen  minutes  for  an  hour  and  a  half  be- 
fore examining,  is  usually  sufficient,  and  the  ef- 
fects of  this  drug  pass  off  in  about  four  days'  time. 

In  these  cases  of  muscular  insufficiencies,  just 
cited,  you  will  observe  that  the  vision  in  each  case 
was  normal,  or  in  other  words,  that  the  eyes  were 
emmetropic.  This  is  by  no  means  always  the  case, 
as  in  the  great  majority  of  cases  of  muscular  insuf- 
ficiency, some  error  in  refraction  is  found,  and 
there  is  one  thing  to  be  borne  in  mind,  and  that  is, 
always  correct  your  refractive  error  of  whatever 
variety,  fully  and  completely,  before  testing  for 
muscle  trouble.  Many  cases  where  a  refractive  er- 
ror is  found  to  exist,  together  with  a  deficiency  of 


ILLUSTRATED  CASES.  181 

muscular  co-ordination,  all  that  will  be  found  ne- 
cessary is  to  correct  the  error,  when  the  muscular 
equilibrium  will  be  sufficiently  restored,  to  remove 
all  causes  of  asthenopia. 


CHAPTER  XIV 


Diseases  aucl  Therapeutics  of  the  Eye, 

It  was  not  our  original  intention  to  say  any- 
thing in  regard  to  the  diseases  of  the  eye  and  their 
treatment,  but  after  considering  the  matter  pro 
and  con,  we  have  concluded  to  add  a  chapter  on 
this  subject,  believing  that  it  will  not  be  amiss  in 
a  little  work  of  this  kind.  In  doing  this,  we  shall 
ha^e  to  abandon  the  catechismal  plan  that  we 
have  adojDted  in  the  preceding  chapters,  as  it 
would  be  difficult  to  adhere  to  that  method  with- 
out going  into  the  subject  too  deeply. 

Our  aim  shall  be  to  simply  point  out  the  prin- 
cipal characteristics  of  the  more  common  diseases 
of  the  different  parts  of  the  eye,  with  a  few  simple 
suggestions  in  regard  to  their  recognition  and 
treatment,  as  it  is  a  matter  of  prime  importance  in 
connection  with  refractive  work  to  be  able  not  only 
to  recognize,  but  diagnose  inflammatory  condi- 
tions. 

For  the  benefit  of  those  of  our  readers  who  are 
not  physicians,  we  will  say  that  the  suffix  "itis" 

182 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     183 

means  inflammation,  and  wherever  it  is  used  in 
connection  with  the  name  of  any  i3articular  part  of 
the  eye,  it  means  an  inflammation  of  that  part;  for 
example,  conjunctiyitis  means  an  inflammation  of 
the  conjunctiva,  either  of  the  eyes  or  lids  or  both. 
Iritis  means  inflammation  of  the  iris,  while  retin- 
itis means  inflammation  of  the  retina. 

There  are  three  varieties  of  inflammation  as 
it  occurs  in  the  different  parts  of  the  eye  as  in  oth- 
er localities,  namely :  acute,  sub-acute  and  chronic. 
Acute  inflammation  of  almost  any  part  of  the  eye 
is  accompanied  by  pain,  redness,  or  congestion, 
photophobia,  or  a  dread  of  the  light,  and  lachry- 
mation,  or  tearing  of  the  eye. 

Many  patients  suffering  with  a  chronic  in- 
flammatory condition  of  the  eyes  are  the  victims 
of  refractive  errors,  and  this  must  be  carefully  cor- 
rected before  we  can  expect  to  cure  the  inflamma- 
tory condition,  as  many  of  these  conditions  are  not 
only  caused  by  refractive  error,  but  the  asthenopia, 
or  eye-strain,  tends  to  keep  it  up,  and  the  first  step 
in  the  treatment  of  these  cases  is  the  removal  of 
the  exciting  cause  by  a  proper  correction  of  the 
refractive  error.  This  is  especially  true  of  ble- 
pharitis marginalis,  or  inflammation  of  the  lids, 
with  the  formation  of  little  crusts  which  mat  the 
cilia,  or  eye-lashes,  together,  and  provoke  a  very 


184    REFRACTIVE  AND  0PHTHAL31IC  CATECHISM. 

uncomfortable  condition  of  affairs.  This  is  also 
true  of  hordeolum,  or  stye  as  it  is  called,  and  chal- 
azion, as  well  as  many  recurring  corneal  inflam- 
mations. 

Many  of  these  cases  can  be  examined  for  the 
purpose  of  determining  their  refractive  condition 
while  still  suffering  from  a  low,  or  chronic,  form  of 
inflammation;  but  there  is  one  point  which  I  wish 
to  impress  upon  your  minds,  and  that  is  never  sub- 
ject an  acutely  inflamed  eye  to  an  examination  for 
the  purpose  of  finding  out  whether  or  not  it  needs 
a  glass.  This  may  seem  an  unnecessary  warning, 
but  I  have  in  mind  the  case  of  a  lady  who  consulted 
me  for  sore  eyes.  She  told  me  that  her  eye  had 
been  troubling  her  for  four  days,  and  that  the  day 
previous  she  consulted  an  optician  who  told  her 
all  she  needed  was  a  pair  of  glasses,after  an  exam- 
ination which,  she  said,  extended  over  an  hour. 
On  looking  at  her  eye  I  found  her  suffering  from  a 
severe  attack  of  acute  iritis,  and  how  much  she  suf- 
fered during  that  previous  examination  can  be  bet- 
ter imagined  than  described. 

The  use  of  the  ophthalmoscope  or  other  re- 
flected light  should  also  be  studiously  avoided  dur- 
ing an  acute  attack  of  inflammation,  except  when 
it  is  absolutely  essential,  as  in  acute  glaucoma  and 
a  few  other  conditions. 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     185 

With  these  few  general  observations  which 
are  intended  for  the  optician,  rather  than  the  phy- 
sician, we  will  pass  to  the  consideration  of  the  dif- 
ferent diseased  conditions,  only,  however,  point- 
ing them  out  in  a  general  way,  without  any  inten- 
tion of  treating  them  in  a  thorough  or  exhaustive 
manner. 

The  first  subject  to  engage  our  attention  is  in- 
flammatory condition  of  the  eye-lids.  As  being- 
appendages  of  the  eye  and  frequently  the  seat  of 
inflammation,  it  is  incumbent  on  us  not  only  to  be 
able  to  recognize  them,  but  also  to  diagnose  the 
different  forms. 

The  eye-lids  are  frequently  the  seat  of  deformi- 
ties, such  as  turning  out  or  an  eversion  of  the 
edges,  called  ectropion.  This,  however,  is  not  so 
frequent  a  condition  as  an  inversion  of  the  lids,  or 
entropion.  The  lids  are  frequently  seen  to  droop 
either  from  a  redundancy  of  tissue  or  paralysis. 
This  is  called  ptosis.  These  conditions  are  only 
amenable  to  surgical  operations.  The  lids  may  be 
the  seat  of  abscess,  or  phlegmon  which  must  be 
treated  as  in  other  parts,  by  hot  applications  and 
the  knife  as  soon  as  it  is  in  a  condition  to  open. 
Boils,  or  furuncles,  may  also  occur,  which  must  be 
treated  in  like  manner. 

Stye,  or  Hordeolum,  is  a  small  boil  on  the  mar- 
gin of  the  lid  generally,  which  must  be  treated  by 


186    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

hot  applications  in  form  of  poultices,  or  hot  solu- 
tions of  boracic  acid  until  they  are  in  a  condition 
to  open  or  break  of  their  own  accord,  which  fre- 
quently they  do. 

Chalazion  is  a  cyst  of  the  Meibomian  glands. 
also  called  tarsal  tumors.  They  are  caused  by  the 
closing-  up  of  the  mouth  of  these  glands  from 
chronic  inflammation  generally.  The  treatment 
generally  consists  in  remoying  them  with  the 
knife,  though  the  frequent  application  of  a  hot  bo- 
racic acid  solution  sometimes  causes  them  to  be 
absorbed. 

Blepharitis,  as  we  haye  seen,  is  a  chronic  in- 
flammation of  the  edge  of  the  lids.  It  is  frequent- 
ly caused  by  a  refractiye  error  Ts4iich  should  al- 
ways be  corrected,  when  undertaking  the  treat- 
ment of  this  trouble.  A  good  ointment  for  this 
condition  is  as  follows :  Yelloy\'  oxide  of  mercury, 
3  grs.,  ung.  petroleum  opt.,  1  oz.  (yaseline.)  Aj)- 
ply  morning  and  night  by  rubbing  well  into  the 
edge  of  the  lids. 

Inflammation  of  the  coujunctiya,  or  conjunc- 
tiyitis,  as  it  is  called,  is  a  frequent  condition.  It 
exists  in  one  of  three  forms  generally.  The  mild 
form,  or  catarrhal  conjunctiyitis,  or  the  more  se- 
yere  form  of  a  muco-purulent  inflammation,  or  un- 
der the  still  more  severe  form  of  purulent  conjunc- 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     187 

tivitis,  generally  infectious.  There  is  also  anoth- 
er distinct  form  of  conjunctivitis  occurring  in  dif- 
ferent degrees  of  severity  and  called  granular  con- 
junctivitis, or  granulated  lids.  The  two  mildest 
forms,  that  is  the  catarrhal  and  muco-purulent 
conjunctivitis,  may  be  confined  to  the  palpebral 
conjunctiva  alone,  or  may  involve  the  ocular  con- 
junctiva also.  It  generally  calls  for  some  mild  as- , 
tringent  application  like  alum  pencil  or  weak  solu- 
tion of  zinc  sulphate,  2  grs.  to  the  oz.  of  distilled 
water,  dropj)ed  into  the  eye  three  times  a  day;  or  a 
good  eye-v>'ater  may  be  made  from  the  following 
prescription : 

Soda  Bi borate,  10  grains. 
Aqua  camphora,  4  drams. 
Aqua  rosa,  4  drams. 

One  or  two  drops  in  the  eye  every  four  hours. 

Purulent  conjunctivitis,  or  ophthalmia,  as  it 
is  called,  calls  for  the  most  intelligent  and  persist- 
ent treatment.  Atropine  sulphate  solution,  4grs. 
to  the  oz.,  should  be  instilled  into  the  eye  at  least 
three  times  a  day  in  all  cases  occurring  in  young 
persons.  This,  how^ever,  must  be  carefully  handled 
in  elderly  persons  if  used  at  all.  Cold  application 
from  ice  must  be  kept  constantly  applied  in  the 
first  stages.  Frequent  and  thorough  cleansing 
w^ith  boric  acid  solution  every  hour,  and  nitrate  of 


188    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

silver  solutions,  5  grs.  to  the  oz.,  must  be  carefully 
brushed  on  the  lids  at  least  once  a  day.  This  must 
be  carefully  done  if  there  is  any  brasion  of  the  cor- 
neal tissue.  The  fellow  eye,  if  not  already  in- 
volved, must  be  carefully  protected  from  infection, 
as  also  the  eyes  of  nurses  or  any  one  having  any- 
thing to  do  with  it. 


When  this  form  of  inflammation  occurs  in 
the  new-born,  as  it  frequently  does,  it  is  called  oph- 
thalmia neonatorum.  Granular  conjunctivits  oc- 
curs in  all  degrees  of  severity,  from  a  few  sand-like 
granulations  of  the  lower  lids  to  the  most  severe 
form  of  lid  deformities  and  blindness.  It  calls  for 
the  most  careful  and  persistent  treatment,  from 
the  application  of  weak  astringent  solution  to  the 
scraping  of  the  lids  (curetting  or  grattage,  as  it  is 
called.)  When  the  scar  tissue  resulting  from  se- 
vere granulation,  causes  incurvation  of  the  lids,  it 
is  called  trachoma,  and  this  generally  gives  rise  to 
a  disease  of  the  cornea,  as  a  result  of  irritation, 
called  pannus,  which  is  caused  by  the  development 
of  blood  vessels  in  the  cornal  tissue.  This  is  a  very 
unfortunate  condition,  and  very  often  results  in 
total  blindness.  This  condition  generally  occurs  in 
persons  of  a  scrofulous  nature,  and  their  general 
constitutional  condition  must  not  be  overlooked  in 
the  treatment. 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     189 

The  treatment  of  granulated  lids  must  be 
carefully  and  scientifically  carried  out.  In  mild 
forms  the  alum  pencil  can  be  thoroughly  applied 
or  the  blue  pencil  (sulphate  of  copper)  may  be  very 
lightly  applied  after  applying  a  solution  of  co- 
caine, 4  grs.  to  the  oz.  This  pencil  must  be  handled 
with  great  care  if  you  wish  to  retain  the  confidence 
of  your  patient.  It  is  a  very  painful  treatment  and 
must  be  used  sparingly.  Solutions  of  nitrate  of 
silver,  3  to  5  grs.  to  the  oz.;  sulphate  zinc  solutions, 
2  grs.  to  the  oz.;  and  many  others  may  be  used. 

A  good  collyrium,  or  eye-water,  is  made  in  the 
following  manner: 

Soda  biborate,  10  grains. 
Acid  tannici,  10  grains. 
Glycerine,  2  drams. 
Aqua  dist.  q.  s.  ad.  1  oz. 

One  or  two  drops  in  the  eye  three  times  a  day. 
This,  I  believe,  is  ,  the  late  Dr.  Agnew's  formula. 
For  the  further  treatment  of  this  condition,  I  must 
refer  you  to  the  more  exhaustive  works  on  this  sub- 
ject, as  we  must  be  content  with  a  general  outline 
only. 

Catarrhal  inflammation  of  the  lids  or  extend- 
ing up  the  nose,  frequently  results  in  a  blocking  up 
of  the  lachrymal  duct.  This  may  remain  in  a 
chronic  condition,  simply  giving  rise  to   obstruc- 


190    REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

tion,  which  results  in  the  tears  flowing  oyer  the  lids 
onto  the  face,  constituting  a  w^eeping,  or  tearing 
eye,  as  it  is  called.  It  may  result  in  an  attack  of 
acute  inflammation  with  the  formation  of  pus,  that 
ma}'  form  a  large  swelling  at  the  inner  canthus  of 
the  lid,  or  may  discharge  itself  on  the  cheek.  This 
is  a  painful  condition,  and  is  called  dacryocystitis. 
This  can  generally  be  determined  by  pressing  over 
the  lachrymal  sac,  ^\  hen  the  pus  is  discharged  into 
the  eye.  This  is  freqiiently  the  cause  of  a  chronic 
conjunctivitis,  and  must  be  corrected  by  incisions 
into  the  sac  and  probing  of  the  duct.  The  milder 
forms  can  generally  be  corrected  by  treating  the 
catarrhal  condition,  and  probing  the  puncta  with 
a  small  probe.  In  the  severer  forms,  repeated 
probing  with  a  probe  gradually  increased  in  size, 
is  necessary  after  first  opening  it  with  a  canalicu- 
lus knife  used  for  this  purpose.  P^equent  injec- 
tion by  means  of  a  lachrymal  syringe  and  some- 
times the  introduction  of  a  silver  tube  or  wire  is 
necessary.    I  prefer  the  latter  myself. 

Inflammatory  disease  of  the  cornea,  either 
acute,  sub-acute,  or  clironic,  is  very  frequently  met 
with,  and  though  the  different  forms  of  corneal 
inflammation  number  a  great  many,  they  are  all 
known  under  the  general  head  of  keratitis,  and  we 
shall  endeavor  to  give  a  general  description  of  the 
varieties  most  frequently  met  with. 


DISEASES  AND    THERAPEUTICS  OF  THE  EYE.     191 

They  are  all  eliaracterized  by  more  or  less 
spasm  of  the  eye-lid,  dread  of  light,  laehrymation, 
pain  and  infiammation,  not  only  of  the  cornea,  but 
of  the  ocular  and  palpebral  conjunctiva  as  well. 

Phlycteuaular  keratitis  is  characterized  by 
the  formation  of  one  or  more  vesicles,  or  blister- 
like imstiiles  on  the  cornea,  generally  at  its  junc- 
tion with  the  sclera,  though  they  may  be  at  any 
other  part  of  the  cornea.  It  is  essentially  a  disease 
of  childhood,  but  may  occur  in  the  adult.  The 
treiftment  consists  in  washing  the  eye  frequently 
with  a  boric  acid  solution,  1  dram  to  the  pint,  and 
the  instillation  of  a  solution  of  atropine,  2  grs.  to 
the  oz.,  to  overcome  the  blephorospat^m,  and  ciliary 
spasiii,  usual  in  these  cases.  An  ointment  of  yel- 
low oxide  of  mercury,  not  stronger  than  4  grs.  to 
the  oz.,  may  be  used  inside  the  lids,  or  the  follow- 
ing combination  can  be  us-ed  in  the  form  of  an  oint- 
ment three  times  a  day: 

Atropine  sulphate,  2  grs. 

Yellow  oxide  of  mercury,  3  grs.,  and 

Vaseline,  1  oz. 

This  must  be  thoroughly  mixed  or  you  will  get 
considerable  smarting  after  using  it. 

The  general  health  of  the  patient  must  be 
carefully  looked  after,  as  they  are  usually  strum- 
ous, and  the  syrup  of  the  iodide  of  iron  in  doses 


193    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

from  5  to  20  drops,  according  to  the  age,  may  be 
given,  well  diluted  in  Avater,  after  each  meal. 

Ulcerative  keratitis  occurs  in  several  forms  in 
poorly-fed  and  strumous  patients.  The  local  treat- 
ment is  about  the  same  as  in  phlyctenular  kerati- 
tis, special  attention  being  paid  to  the  general 
health.  These  ulcers  may,  however,  occur  at  auy 
age,  and  in  elderlj^  persons  atropine  must  be  care- 
fully j)rescribed  for  fear  of  any  glaucomatous 
complications. 

Hypopyon  keratitis,  is  keratitis  in  which  pus 
forms  and  falls  to  the  most  dependent  part  of  the 
anterior  chamber  of  the  eye.  This  is  generally  ab-' 
sorbed,  though  it  may  be  necessary  to  evacuate  by 
means  of  the  knife.  Hot  applications  assist  in  ab- 
sorbing this  pus,  but  poulticing  must  be  avoided, 
as  it  ma}'  do  much  injury,  and  rarely,  in  any  case, 
much  good.  Hot  boric  acid  solution  will  be  found 
to  answer  all  i)urposes  of  this  kind,  or  hot  bichlor- 
ide of  mercury  solutions,  1  to  10,000,  may  be  used 
instead. 

Interstitial  keratitis.  This  is  a  circumscribed, 
or  diffused,  inflammation  of  the  corneal  tissue,  not 
usually  accompanied  by  any  ulceration,  and  the 
character  of  the  inflammation  may  be  quite  acute 
or  very  low  and  chronic.  It  is,  in  a  great  majority 
of  cases,  caused  by  syi^hilis,  either  inherited  or  ac- 


DISEASES  A^^D  THERAPEUTICS  OF  THE  EYE.     193 

quired.  It  may  inyolve  only  a  part  of  the  cornea, 
or  continue  until  the  whole  cornea  is  involved.  The 
cornea  becomes  hazy  if  not  opaque,  and  total  blind- 
ness may  result.  It  is  most  frequent  in  young  life. 
The  treatment  is  princix3ally  constitutional;  mer- 
cury and  iodide  of  potash,  cod  liver  oil,  iron,  etc. 
Irritating  applications  must  be  avoided.  They  gener- 
-ally  get  well  under  jDroper  constitutional  treat- 
ment, but  it  requires  a  long  time  to  fully  recover. 

As  a  result  of  many  of  these  corneal  inflam- 
mations, scars  or  small  opacities,  are  left  on  the 
cornea,  and  if  they  be  central,  or  over  the  pupil, 
may.  interfere  ^-^ery  materially  with  vision.  When 
they  are  not  over  the  puinl,  they  may  be  a  cause  of 
irregular  astigmatism.  It  is  these  opacities  on  the 
cornea  that  are  frequently  called  cataracts  by  the 
laity,  and  they  will  call  on  you  many  times  to  have 
them  removed,  as  if  it  were  a  simple  matter.  These 
slight  opacities,  or  scars,  can  be  nicely  seen  by 
oblique  illumination,  which  consists  in  condens- 
ing with  a  convex  lens  the  light  on  the  cornea,  the 
source  of  illumination  being  to  the  side  of  the  pa- 
tient. 

Little  spots  on  the  cornea  that  can  hardly  be 
detected  by  the  ordinary  method,  can  be  readily 
seen  in  this  way. 


194     REFRACTIVE  AXD  OPHTHALMIC  CATECHISM 

Iritis,  or  inflammation  of  the  iris,  is  frequent- 
ly met  with  as  a  result  of  rheumatism,  syphilis, 
and  other  causes,  and  should  be  recognized  in  the 
very  beginning.  There  is  inflammation  of  the  cor- 
junctiva,  a  tortuous  condition  of  the  blood  vessels 
in  the  ocular  conjunctiva,  pain  over  the  eye,  ex- 
tending to  the  side  of  the  head,  many  times.  The 
pupil  is  generally  small,  and  there  is  great  dread 
of  the  light,  as  well  as  lachrymation.  By  having 
the  j)atient  look  down  and  gently  pressing  with  the 
tips  of  your  index  fingers,  a  very  tender  spot  will 
always  be  found  at  about  the  upper  edge  of  the 
cornea.  This  is  almost  characteristic  of  iritis,  and 
should  be  always  looked  for  when  this  disease  is 
suspected. 

The  local  treatment  of  iritis  is  atropine  first, 
last,  and  always,  and  it  should  be  used  in  the  very 
beginning  before  any  adhesion  takes  place  be- 
tween the  iris  and  the  anterior  capsule  of  the  lens. 
When  this  does  occur,  they  should  be  broken  up 
by  the  use  of  atropine,  if  possible.  Generally  a  so- 
lution of  4  grs.  to  the  oz.  is  sufficient,  used  every 
two  hours,  if  necessary.  Boric  acid  solutions  can 
also  be  used,  as  well  as  any  constitutional  treat- 
ment indicated.  These  cases  should  be  recognized 
in  the  beginning,  as  in  that  way  you  can  often  save 
your  patient  a  long  siege  of  suffering.  Of  course, 
it  is  necessary  to  protect  the  eyes  from  strong 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     195 

lights,  but  do  not  bandage  the  eye  up  too  much,  as 
it  does  better  when  having  good  ventilation.  Nev- 
er use  poultices  in  iritis.  Sometimes  it  is  neces- 
sary to  use  eserine  from  time  to  time,  in  these 
cases,  and  when  occurring  in  elderly  persons,  the 
atropine  must  be  closely  watched,  for  there  is  al- 
ways the  probability  of  its  being  complicated  by 
glaucoma. 

Diseases  of  the  crystalline  lens,  such  as  lenti- 
cular opacities,  or  cataractous  metamorphosis,  can 
be  readily  detected  by  means  of  the  ophthalmo- 
scope, and  as  very  little  practice  is  all  that  is  ne- 
cessary, we  shall  not  enter  into  a  description  of  its 
use,  but  refer  the  reader  to  the  chapter  on  the  use 
of  the  ophthalmoscope.  Opacities  of  the  vitrious 
humor  and  disease  of  the  retina  and  optic  nerve 
are  also  to  be  detected  with  the  ophthalmoscope. 

There  is  one  other  diseased  condition  of  the 
eye  to  which  I  shall  call  your  attention,  and  which 
it  is  absolutely  essential  that  every  person  having 
anything  to  do  with  the  eye  should  be  able  to  di- 
agnose, as  an  early  recognition  may  be  the  only 
means  of  saving  your  patient's  eye-sight.  I  refer 
to  glaucoma,  or  an  increased  hardness  of  the  eye- 
ball, caused  by  a  blocking  up  of  its  excretory  ca- 
nal. This  condition  of  glaucoma  may  exist  in  any 
one  of  three  forms.  It  may  be  acute,  sub-acute,  or 
chronic.    The  intra-ocular  tension  may  be  slight, 


196    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

SO  as  to  be  scarcely  recognizable  by  the  tips  of 
your  index  fingers  pressed  gently  onto  the  globe  of 
the  eye;  or  it  may  be  very  hard.  This  is  an  impor- 
tant symptom.  The  pnpil  is  generally  dilated  and 
does  not  respond  readily  to  light.  The  lens  is 
pressed  forward  into  the  anterior  chamber  of  the 
eye,  rendering  it  shallow.  There  is  generally  a 
partial  loss  of  transparency  of  the  cornea.  The 
pressure  behind  produces  a  cupping  of  the  nerve- 
head,  seen  with  the  ophthalmoscope,  and  the  blood 
vessels  climb  over  the  edge  of  the  disk,and  are  seen 
to  pulsate.  The  field  of  vision,  as  measured  by  the 
perimeter,  is  contracted,  though  central  vision 
may  be  good  at  the  time  of  examination.  The 
cornea  is  not  nearly  as  sensitive  as  in  health,  and 
one  of  the  characteristic  signs  is  what  is  called 
iridescent  vision,  that  consists  in  a  colored  halo 
surrounding  artificial  lights.  This  point  should 
always  be  borne  in  mind. 

There  is  always  more  or  less  pain,  according 
to  the  acuteness  of  the  attack,  and  the  invasion  of 
the  disease  may  be  so  severe  as  to  destroy  the  sight 
in  twenty-four  hours;  hence  the  necessity  of  re- 
cognizing it  at  once.  There  may  be  repeated  at- 
tacks of  the  sub-acute  variety,  and  the  chronic 
form  may  last  for  years.  It  may  be  confined  to  one 
eye  or  involve  both,  and  is  rarely  seen  before  the 
fortieth  year.    You  must  never  use  atropine  or 


DISEASES  AND  THERAPEUTICS  OF  THE  EYE.     197 

other  m^'driatic  when  you  have  any  reason  to  sus- 
jject  glancoma,  as  this  would  only  make  it  worse. 
Eserine  sulphate,  1  gr.  to  the  oz.,  or  muriate  of 
pilocarj^in,  2  gr.  to  the  oz.,  may  be  instilled  into  the 
eye  every  four  hours,  and  hot  boric  acid  solution 
may  be  applied;  but  in  many  cases  the  only  hope  in 
saving  the  eye  rests  in  the  early  performance  of 
the  operation  known  as  iridectomy. 

The  destructive  tendency  of  glaucoma  ren- 
ders it  an  alarming  condition,  and  it  is  of  the  ut- 
most imiDortance  that  it  be  early  recognized  in  or- 
der to  give  the  patient  the  very  best  chance  of  re- 
covery; hence  the  necessity  of  becoming  familiar 
with  its  early  symptoms. 

The  ophthalmoscopic  diseases  of  the  eye  we 
shall  not  consider,  as  they  are  interesting,  gener- 
ally, only  to  the  specialist  who  will  not  look  to  a 
little  work  of  this  kind  for  information  to  be  had 
in  any  of  the  more  complete  works  on  diseases  of 
the  eye. 

A  few  words  in  regard  to  the  removal  of  for- 
eign bodies  from  the  eye.  It  is  always  best  to  keep 
on  hand  a  4  per  cent,  solution  of  cocaine  for  this 
purpose.  A  few  drops  instilled  into  the  eye  will 
render  it  anaesthetic,  and  you  can  manipulate 
with  the  greatest  ease  and  without  hurting  your 
patient  in  the  least,  a  very  important  matter,  as 


198      REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

far  as  tbev  are  concerned.  It  generally  causes  a 
transitory  dilatation  of  the  pupil,  but  this  will  pass 
away  in  a  short  time.  Foreign  bodies  lodged  on 
the  cornea  can  be  remoyed  by  the  means  of  a  si)ud, 
while  those  finding  lodgment  under  the  lids  can 
be  remoyed  by  first  eyerting  the  lids,  and  wiping 
them  off  by  means  of  a  little  cotton,  wrapped  on 
the  end  of  an  ordinary  applicator  or  tooth-i3ick. 
Care  must  always  be  taken  in  remoying  foreign 
bodies  from  the  cornea,  not  to  injure  the  corneal 
tissue  but  as  little  as  possible,  and  your  instru- 
ment must  always  be  clean,  or  you  may  infect  the 
wound,  and  produce  a   seyere  corneal  ulceration. 


GLOSSARY. 


ACHROMATOPSIA— Inability  to  distinguish 
colors. 

ABDUCTION— The  turning  out  of  the  eye-ball. 

ADDUCTION— The  turning  in  of  the  eye-ball. 

ALBINISM — The  absence  of  pigment  in  the  iris 
and  choroid,  as  well  as  other  parts  of  the 
body. 

AMAUBOSI^^— Loss  or  dimness  of  sight. 

AMBLYOPIA — Same  as  Amaurosis. 

ANAESTHESIA — Loss  of  sensation,  either  par 
tial  or  complete. 

ANISOMETROPIA— A  different  refractive  con- 
dition in  each  eye,  either  hyperopic  or  myopic. 

ARCUS  SENILIS— A  ring  formed  around  the 
outer  edge  of  the  cornea,  usually  seen  in  old 
age. 

ARGYLL— ROBINSON  PUPILS  —  Contracted 
pupils  found  in  spinal  disease;  pupils  unaf- 
fected by  light,  but  contracting  still  more  on 
converging  visual  axes. 

199 


300    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

ASTIGMATISM— A  difference  in  the  curvatiire 
of  tlie  different  meridians  of  the  cornea  or 
lens. 

ASTHENOPIA — Eye  strain  from  any  cause. 

BLEPHAEITIS— Inflammation  of  the  edge  of  the 
eye-lids. 

BLIXD  SPOT,  MAERIOTTS— A  spot  on  the  reti- 
na corresponding  with  the  entrance  of  the  op- 
tic nerve. 

CATAEACT — An  opacity  of  the  crystalline  lens. 

CENTEAD— Standard  used  by  Dr.  Dennett  for 
measuring  prisms. 

CHALAZIOX— A  little  humor  on  the  lids;  also 
called  tarsal  tumors. 

CHEMOSIS — A  swelling  of  the  conjunctiva,  gen- 
erally the  result  of  disease. 

CHOEOID — The  middle  coat  or  tunic  of  the  eye- 
ball. 

CHOEOIDITIS— Inflammation  of  the  choroid. 

CIOATEIX — Scars  from  any  cause. 

CILIAEY  BODY— Formed  by  the  union  of  the  cil- 
iary processes. 

COLOBO^NFA — A  displaced  pupil,  either  congeni- 
tal, or  the  result  of  injury  or  operation  on  the 
iris. 

COLOE  BLINDNESS— Same  as  Achromatopsia. 


GLOSSARY.  201 

CONJUNCTIVA — [Mucous  membrane  covering 
the  eye-ball  in  front  and  the  inside  of  the  eye- 
lids. 

CONJUNCTIVITIS— Inflammation    of    the   con- 
junctiva. 

CORNEA — Anterior  portion  and  transparent  part 
of  the  eve-ball. 

CORNEAL  LOUPE — A  strong  convex  lens  used 
to  examine  the  cornea. 

CYCLITIS — Inflammation  of  the  ciliary  body. 

DACRYOCYSTITIS— Inflammation  of  the  lach- 
rymal sac  and  nasal  duct. 

])AY  BLINDNESS— Inability  to  see  clearly  on 
bright  days,  or  in  a  bright  light. 

DIOPTRE — A  lens  having  a  focal  distance  of  one 
metre:  39.36  inches. 

DIOPTRIC  SYSTEM— Method  of  numbering 
lenses,  according  to  the  dioptre. 

DIPLOPIA — Double  vision;  seeing  two  objects. 

ECTROPION — A  turning  out  or  an  eversion  of 
the  eye-lids. 

EMMETROPIA— A  condition  of  refraction  re- 
garded as  normal, 

ENTROPION — An  inversion  or  turning  in  of  the 
eve-lids. 


20-3    REFRACTIVE  AXD  OPHTHALMIC  CATECHISM. 

EXUCLEATIOX— Removal  of  the  eve-ball. 

EPIPHORIA — An  overflow  of  tears,  a  "weeping" 
or  "tearing'-  eye. 

ESOPHORIA— A  tendency  of  the  eyes  to  turn  in 
from  the  visual  line. 

EXOPHORIA— A  tendency  of  the  eyes  to  turn 
out  from  the  visual  line. 

EX0PHTHAL:MUS— A  protrusion  of  the  eyes 
from  their  orbits. 

FAR  POINT— The  greatest  distance  at  which  an 
eye  can  see  clearly  without  the  aid  of  glasses. 

GLAUCOMA — A  disease  of  the  eye  that  consists 
in  a  hardening  of  the  eye-ball  from  increased 
intraocular  tension. 

GLATTOMATOUS  RING— A  cupping  or  depres- 
sion of  the  nerve  head  seen  with  the  ophthal- 
nifiscope  in  glaucoma. 

GRAXULAR  LIDS— Granular  conjunctivitis. 

11  EMI AXOPSI A— Blindness  involving  one-half 
the  field  of  vision,  either  in  one  or  both  eyes. 

HEMIOPIA— See  Hemianopsia. 

HETEROPHORIA--A  lack  of  muscular  equili- 
brium of  the  eyes. 

HYPER:METR0PIA— A  refractive  condition  of 
the  eye,  in  which  the  principal  focal  point  of 
the  eve  is  behind  the  retina. 


GLOSSARY.  203 

HYPERPnOEIA— A  tendency  of  the  eyes  to  turn 
above  the  visual  line. 

HYPOPYON — A  collection  of  pus  in  the  anterior 
chamber  of  the  eye. 

nORDEOLU3I— See  stye. 

lEIS — A  diaphram  separating  the  crystalline  lens 
from  the  anterior  chamber  of  the  eye,  and 
regulating  the  amount  of  light  admitted  into 
the  eye. 

IRITIS— Inflammation  of  the  iris. 

KERATITIS— Inflammation  of  the  cornea. 

KERATOSCOPE— An  instrument  for  observing 
corneal  astigmatism  or  other  corneal  irregu- 
larities. 

LENS — A  ]Diece  of  glass  or  other  transparent  sub- 
stance, ground  into  various  shape  and  used  to 
change  the  course  of  rays  of  light. 

MACCLA  LUTE  A— The  central  part  of  the  reti- 
na where  images  are  ordinarily  formed. 

MARRIOTT'S  SPOT— See  blind  spot. 

MEDIA — The  refracting  parts  of  the  eye:  Cornea 
aqueous  humer  crystalline  lens  and  vitrious 
humer, 

MEIBOMIAN  GLANDS— Small  gland  found  on 
the  inside  of  the  eye-lids. 


204    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

IMUSCAE  YOLITA:NTEvS— Floating  bodies  or 
black  spots  before  the  eyes. 

MYDRIASIS— Dilation  of  the  pupil. 

MYDRIATICS— Drugs  that  cause  a  dilatation  of 

the  pupil. 

MYOPIA — A  refractive  condition  of  the  eye  in 
which  the  principal  focal  point  of  the  eye  lies 
anterior  to  the  retina. 

MYOTICS — Drugs  that  cause  a  contraction  of  the 
pupil. 

MYOSIS— A  contraction  of  the  pupil. 

NEURITIS— Inflammation  of  a  nerve. 

NIGHT  BLINDNESS— A  functional  disease  of 
the  retina. 

NYSTAGMUS— An  involuntary  movement  of  the 
ele-balls,  oscillatory  in  character  and  usually 
from  side  to  side;  usually  seen  in  albinism. 

OPHTHAL]\riA— Inflammation  of  the  conjunc- 
tiva.   Conjunctivitis. 

OPHTHALMITIS— Inflammation  of  the  eye-ball 
as  a  whole. 

OPHHTALMOMETRE— An  instrument  for  meas- 
uring the  diameters  of  the  eye. 

OPHTHALMOPLEGIA— Paralysis  of  the  mus- 
cles of  the  eye-ball. 


GLOSSARY.  205 

OPHTHALMOSCOPE— An  instrument  for  exam- 
ining the  interior  of  the  eye,  to  determine  its 
condition  as  to  health  and  refraction. 


is 


OPTIO  AXIS — An  imaginary  line  passin 
through  the  center  of  the  cornea  and  lens 
from  an  object  to  the  posterior  pole  of  the  eye- 
ball. 

OPTIC  DISK— The  entrance  of  the  optic  nerve. 

OPTOMETER — An  instrument  for  measuring  the 
refraction  of  an  eye. 

ORBIT — The  bony  cavity  in  which  the  eye-ball  is 
located. 

ORTHOPHORIA— A  normal  equilibrium  of  the 
ocular  muscles. 

PERIMETRE — An  instrument  for  measuring  the 
field  of  vision. 

REFRACTION— A  bending  of  rays  of  light  as 
they  pass  from  one  medium  to  another  of  dif- 
ferent density. 

RETINA — The  inner  coat  or  tunic  of  the  eye;  the 
sensitive  layer. 

RETINITIS— Inflammation  of  the  retina. 

RETINOSCOPE — An  instrument  for  determining 
the  refraction  of  the  eye,  by  reflecting  light 
from  a  given  point  into  the  eye  and  observing 


206    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

its  movement,   as   the   retinoscope  is   moved 
slightly  on  its  different  axes. 

SCLEKA— The  external  coat  of  the  eye. 

SCLEBITIS— Inflammation  of  the  sclera. 

SHADOW  TEST— See  retinoscope. 

SKIASCOPY— See  retinoscope. 

SQUINT— Strabismus. 

STKABISMUS—  Deviation  of  the  eye  from  the 
visual  angle,  either  in  (internal  strabismus) 
or  out  (external  strabismus.) 

STAPHYLOMA  OF  THE  CORNEA— A  projec- 
tion of  the  anterior  chamber  of  the  eye,  by 
rupture  of  some  of  the  corneal  tissue,  usually 
the  result  of  disease. 

STAPHYLOMA  POSTERIOR  —  A  drawing 
away  of  the  retina  from  about  the  optic  nerve 
disk.  Generally  crescent  shaped  and  results 
from  disease  or  high  degrees  of  myopia. 

STYE — A  little  boil  on  the  eye-lid;  also  called 
hordeolum. 

SYNECHIA  POSTERIOR— An  attachment  of 
the  posterior  surface  of  the  iris  to  the  anter- 
ior capsule  of  the  crystalline  lens,  caused  us- 
ually by  iritis. 

TENOTOMY— The  operation  of  cutting  the  ocu- 
lar muscles  for  squint  or  other  purposes. 


GLOSSARY.  207 

TEST  LETTERS— Series  of  letters  of  a  certain 
size  and  shape,  used  to  test  the  acuteness  of 
vision. 

TENSION  OF  THE  EYE— Term  used  to  denote 
the  hardness  of  the  eye-ball. 

YELLOW  SPOT— The  macula  lutea,  or  point 
where  images  are  formed  on  the  retina. 


INDEX. 


A. 


Abscess  of  lids 185 

Abductive  power  of  eye 180 

Accommodation  of  eye 35 

Accommodation,  range  of 34 

Accon'modation,  power  of 34 

Accommodation,  loss  of 38 

Accommodation,  spasm  of 45 

Adductive  power  of  eye 180 

Ametropia 41 

Amblyopia  ex.-anopsia 145 

Anatomy  of  the  eye 9 

Anisometropia 56  to  163 

Artery  carotid 16 

Arteria  centralis  retinae 16 

Artery  ophthalmJc 16 

Asthenopia 41 

809 


210    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Astigmatism 58 

Astigmatism,  causes  of 58 

Astigmatism,  kind  of 58 

Attigraatism,  frequency  of 60 

Astigmatism,  regular 58 

Astigmatism,  irregular 58 

Astigmatism,  simple  hypermetropic 59 

Astigmatism.,  simple  myopic 59 

Astigmatism,  compound  hypermetropic 59 

Astigmatism,  compound  myopic 59 

Astigmatism,  mixed 59 

Astigmatic  chart.  Green's 63 

Atropine  sulpha^te ISO 


B 


Blepharitis  marginalis 186 

Blind  spots 155 

Blind  spot  of  Marriotte 155 

Blood  vessels  of  the  retina 85 

Blue  pencil 189 

Boils 185 

Bright's  disease 84 

C 

Canthus 13 

Camera  obscura 16 

Centrad 27 

Chalazion ' 186 

Choroid 11 

Choroiditis 51 

Choroido  retinitis 156 

Ciliary  processes 11 

Ciliary  muscle , , 12 

Conjunctiva 13 


INDEX.  211 

CoFijunctiva,  ocular .< 13 

Conjunctiva,  palpebral 13 

Conjunctivitis 186 

Conjunctivitis,  catarrhal 186 

Conjunctivitis,  muco  purulent 186 

Conjunctivitis,  purulent 186 

Conjunctivitis,  granular 187 

Copper  sulphate 189 

Crystaline  lens,  diseases  of 195 

Cupping  of  the  nerve  head 196 

Curetting 188 


D 


Dacryocystitis 190 

Diabetis 84 

Dioptric  media 12 

Dioptre 25 

Dioptric  system 25 

Dioptric  table 26 

Diplopia 131 

Diplopia,  monocular 132 

Diplopia,  vertical 131 

Diseases  of  the  eye 182 

Double  vision 131 

B 

Ectropion 185 

Entropion 185 

Emmetropia 39 

Emmetropic  eye 40 

Eserine  sulphate 197 

Esophoria 138 

Eversion  of  the  lids 185 

Exophoria 138 


212    REFRACTIVE  AND  OPHTHALMIC  CATECHISM. 

Eye  strain 41 

Eye  water,  Agnew's 189 

P 

Far-sightedness 42 

Field  of  vision 150 

Field  of  vision,  how  obtained 153 

Fovae  centralis  retinae 17 

Foreign  bodies  in  eye 197 

Foreign  bodies,  removal  of 197 

French  method  of  numbering  lenses 25 

Furuncles 185 

G 

Glaucoma 156,  188,  195 

Glaucoma,  acute 195 

Glaucoma,  sub-acute 195 

Glaucoma,  chronic 195 

Glaucoma,  treatment  of 197 

Glossary 199 

Granulated  lids 187 

Grattage 188 

H 

Homatropine 180 

Hordeolum 185 

Hyoscyamine 180 

Hypermetropia 39 

Hypermetropic  eye 41 

Hypermetropia,  cause  of 43 

Hypermetropia,  kinds  of 43 

Hypermetropia,  axial „ 43 

Hypermetropia,  curvature 43 

Hypermetropia,  manifest 43 


INDEX.  213 

Hypermetropia,  latent 43 

Hypermetropia,  total 46 

Hypo-phoria 138 

Hypo-esophoria 138 

Hypo-exophoria 138 


Index  of  refraction 18 

Index  of  refractive  media 1& 

Index  of  dioptric  media . . . ; 19 

Inversion  of  the  lids 185 

Iris 12 

Iritis 194 

Iritis,  treatment  of 194 

Iridescent  vision 196 

Iridectomy 197 


Jager  type 34 

K. 

Keratoscope,  Placido's 65 

Keratitis 190 

Keratitis,  hypopyon 192 

Keratitis,  interstitial » 192 

Keratitis,  phlyctenular 191 

Keratitis,  ulcerative ■ 191 


Lechrymation 191 

Lachrymal  gland 13 

Lachrymal  sac 14 

Lenses 20 


214    REFRACTIVE  AND    OPHTHALMIC  CATECHISM. 

Lenses,  kinds  of 20 

Lenses,  signs  used  for 21 

Lenses,  cylindrical 22 

Lenses,  cylindrical  axes  of 23 

Lenses,  meniscus 21 

Lenses,  periscopic 21 

Lenses,  spherical 22 


M. 


Macula  lutea 17 

Mad  dock's  test 143 

Meibomian  glands 14 

Mercury  oxide 191 

Muscles  of  the  ej^e 15 

Muscular  asthenopia 131 

Muscular  asthenopia,  evidence  of 136 

Muscular  deficiencies 175 

Myopia 49 

Myopic  eye 49 

Myopia,  causes  of 50 

Myopia,  frequency  of 51 

Myopia,  indications  of 51 

Myopia,  axial 50 

Myopia,  curvature 50 

Myopia,  correction  of 50 


N. 


Nerves  of  the  eye 16 

Nerves,  second  or  optic 16 

Nerves,  third  or  motor  oculi 16 

Nerves,  fourth  or  trochlear 16 

Nerves,  sixth  or  abduceus 16 

Nerves,  cupping  of  optic 196 


INDEX.    .  215 

O. 

Obpects  distortion  of 72 

Opacities  of  the  eye 193 

Ophthalmia 187 

Ophthalmoscopy 78 

Ophthalmoscope 78 

Ophthalmoscope,  Loriiig's 79' 

Ophthalmoscope,  uses  of 80 

Ophthalmoscope,  direct  method  of  use 83 

Ophthalmoscope,  indirect  method  of  use 84 

Ophthalmoscope  in  emmetropia 89 

Ophthalmoscope  in  hypermetropia 90 

Ophthalmoscope  in  hypermetropic  astigmatism    91 

Ophthalmoscope  in  myopia 91 

Ophthalmoscope  in  myopic  astigmatism 94 

Ophthalmometry 96 

Ophthalmometre,  Javal  &  Schiotz 97 

Orbits  of  the  eye 9 

Orbicularis  palpebrarum 10 

Opticum  dextrum 45 

Opticum  senistrum 45 

Optic  disk 52 

Orthophoria 140 


P. 


Pannus 188 

Papillitis 156 

Perimetry 150 

Perimeter,  Skeel's 152 

Perimeter  charts 154 

Phorometer,  Wilson's 149 

Phlegmon 185 

Pilocarpine  muriate 197 


216    REFRACTIVE  AND    OPHTHALMIC  CATECHISM. 

Placido's  keratoscope 65 

Presbyopia 122 

Presbyopia,  cause  of 123 

Presbyopia,  correction  of 123 

Presbyopia,  when  developed 123 

Presbyopia,  with  ametropia 125 

Presbyopia,  with  hypermetropia 125 

Presbyopia,  with  astigmatism 127 

Presbyopia,  myopia  delays 129 

Prism  dioptre 27 

Puncta  lachrymalia 14 

Punctum  proximum 34 

Piinctum  remotum 34 

Pupil 12 

Ptosis 185 


R. 


Refractive  media 12 

Refraction  and  lenses 18 

Ref ractometer,  DeZeng's 77 

Retina 11 

Retinoscopy 106 

Retinoscopic  mirror  plane 107 

Retinoscope  in  hypermetropia 110 

Retinoscope  in  astigmatism 120 

Retinoscope  in  myopia 110 

Retinitis 156 

Reversal  point 114. 

Retinal  reflex 109 

S. 

Scars 193 

Sclera 11 

Scleritis 51 


INDEX.  217 

Scotoma 155 

Section  of  eye-ball 10 

Second  sight 57 

Shadowiest 106 

Silver  nitrate : 189 

Skiascopy 106 

Skeel's  perimeter 152 

Snellen  type 31 

Strabismus 46 

Strabismus,  convergens 159 

Strabismus,  divergens 52 

Staphyloma  posterior 52 

Stenopaeic  slit 65 

Stenopaeic  slit,  uses 66 

Steven's  system  of  nomenclature 138 

Steven's  phorometer 141 

Steven's  phorometer,  directions 141 

Steven's  stenopaeic  lens  test 142 

Stye 185 

Squint 46 

Suspensary  ligament 11 

T. 

Tarsal  tumors 186 

Tearing  eye 190 

Tension  of  eye-ball 195 

Test  type,  Snellen 30 

Test  type,  Jager 34 

Therapeutics  of  the  eye 182 

Trial  case 29 

Trial  frame 33 

V. 

Visual  angle 30 

Visual  acuteness 32 


218    REFRACTIVE  AND   OPHTHALMIC  CATECHISM. 

Visual  acuteness,  how  obtained 32 

Vision,  binocular 52 

Vision,  double 52 

Vitrious  humor 11 

W. 

Walleston  prism 98 

Weeping  eye 190 

Wilson's  phorometer 149 

Y. 

Yellow  spot 17 


JUST  ISSUED. 


DHIL-EV'S 

REFRACTIVE  AND  OPHTHALMIC  CATECHISM 


I=OR 


01 


Published  by 

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Gloversville,  N.  Y. 

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